The first question many people have is, "With all that Android and Apple smartphones and tablets can do, why would anyone want to use a PDA?" It's a valid question, but there's a valid answer:--three of them, in fact
The Japanese Language Tools system is available on several different platforms. What are the differences between them and which one is right for you? Here's a quick summary of each; for more information you can see the reviews and spec sheets I've linked to, and of course you can find more online.
Dell Axim X51V: Review, Spec Sheet
This is the PDA I recommend for most users. In all the important specifications, the X51V is still at the top of the class, even when looking at the newest 2011 models. Because of the way the touchscreen works, it's far better for inputting kanji than those of most current devices; devices with "multitouch" screens like the iPhone are especially bad for this. The X51V has been refurbished to working like-new condition, and indeed it performs and lasts like brand new. All of the working parts subject to wear and tear have been replaced with brand new parts, including most importantly the touchscreen. The body of the Axim will likely show signs of use, as replacement body shells are no longer available--there may be a few scuffs and scratches but it will look pretty good. All the other components are thoroughly tested and replaced if they don't perform like new. This allows me to sell a PDA with top-of-the-line features in functionally new condition for much less than the system would cost with an equivalent new PDA, smartphone, or tablet. These refurbished Axims have proven rock solid. The size is just right--being able to carry it comfortably in my pocket means it's there when I need it--a PDA that isn't is no good to me at all. Battery life is more than sufficient for a full day of normal use (~3-4 hours total on-time on normal settings with dictionary lookups, study with a flashcard program, some time online via Wi-Fi, wasting some time on games, etc.; about 9-10 hours just listening to music with the screen off). Double-size batteries are available for the Axim, though I think it's more practical to simply carry a tiny, matchbook-sized spare if you really think you'll need more power (though, to be honest, most customers who buy a spare battery never end up needing it).
My favorite non-dictionary use: the Axim is my GPS navi unit when hiking and driving. Unlike phone-based GPS navigation systems that are becoming popular, this one works wherever you go (the phone-based units pull their maps from the cellular network--which means that, outside the 3G signal areas, they simply don't work, and even in covered areas you spend a lot of time waiting for maps to load as you drive). And the maps on the Axim are far more detailed out in rural and wild areas.
Big note: The Dell Axim X51V as it was originally released was a great piece of hardware crippled by the horrible Windows Mobile 5 operating system. JLT has upgraded the OS to WM6, and now the Axim really flies. It's as fast and stable as anything on the market. WM6 also allows the Axim to use SDHC cards in the SD card slot, increasing the memory capacity in that slot to 32 GB (a 32 GB card comes with the JLT system). Like all the others, it can also take up a 128 GB CF card, too, for a total capacity of 160 GB. WM6 also simplifies software installation and memory handling, and includes much better versions of the Microsoft Office applications (Word, Excel, PowerPoint, etc.) than WM2003SE on the Axim X30 and iPAQ hx4700. There are hundreds of thousands of programs available for the Windows Mobile OS--you can do anything from align a telescope to control your TV, from talk on Skype to practice Lithuanian verb declensions.
Besides upgrading the Axim to WM6, I've also customized the OS to offer full Japanese support, using the same systems used in the native Japanese version of WM. Japanese input and display look and work exactly like they do on native-Japanese PDAs (and better than they do on most native-Japanese phones). This means that they're part of the OS, so they're fully integrated and usable in every program and they work beautifully. So you get both the superb Japanese support you'd find in a native Japanese device and the ease of use of an English language operating system--the best of both worlds.
As a bonus, the 32 GB card included standard with the system has more than enough space for me to include the full text of both the English and Japanese versions of Wikipedia, so you can access that even without an internet connection. (Those are free and not my work--just some of many cool things you can find for the Axim).
Included Accessories: 32 GB SDHC card; USB SDHC card reader; JLT documentation, Dell Owner's Manual, and backups on DVD; generic screen protector; soft slip case; stylus; battery, power supply; deluxe sync/charge cable; 30 day money back guarantee; 1 year hardware warranty; 3 years support.
Dell Axim X30: Spec Sheet.
The main point is that, while built on a more basic PDA, as a dictionary the X30 system works just like the other JLT Complete Systems: it uses the same dictionaries and dictionary program and has the same Japanese input systems (Japanese OS version) or very similar ones (English OS version with ATOK input software). The average user will also have no problem using the built-in organizer features (calendar and appointment book, task list, alarm clock, phone book), voice recorder, and portable MS Office apps to read and do simple editing of MS Office documents (Word docs, Excel spreadsheets). It's also easy to load up a few hundred songs and a few movies for entertainment on the go, and to install additional programs, many free, like different word processors, calculators (a pretty good free one is already installed), simple games, station-to-station route guides for just about every subway system in the world (free program, one-click installer included on the system), and many other things. The X30 also has Bluetooth and Wi-fi and most of the same capabilities as the X51V, but because of the older WM2003SE OS and some hardware limitations, it may be harder to use some of these features unless you've got a good bit of computer savvy (Wi-Fi works right off the bat for about two-thirds of users, but if it doesn't you need to know a bit about networks to be able to change the settings for your network to make it accessible to the X30). Also, the 2.5 GB of free space on the memory card when you get the system (vs. 14 GB for the standard X51V, 155 GB with the maximum memory installed in the X51V) means that extremely memory-intensive things like GPS maps and large audio and video libraries aren't possible. While there are tens of thousands of programs for the X30 (any program that will run on WM2003SE, and most made for later versions of the OS), some Windows Mobile programs work only on later versions of the OS. In short, for the average user, the X30 will probably be more of a dictionary-only system (plus a few basic things like the appointment book, alarm clock, calculator, games, and non-net programs), rather than a multipurpose device like the X51V.
The only noticeable difference for dictionary use is that the screen has lower resolution than the other JLT systems (240 x 320 vs. 480 x 640 for the X51V, etc.), which means characters have to be bigger to be legible because it's not as sharp. The screen is also slightly smaller than those on the other JLT systems (3.5", vs. 3.7" for the X51V and X50V). However, it's still pretty good--much better than displays on standard denshi jisho. Click here to see a comparison of the X30 and X51V screens (actual screenshots). View at full size on your monitor to get the best idea of the relative sharpness, but to really see the real sizes and sharpenesses of the screens, print it out on A4 or letter size paper.
Another difference that has a minor impact on dictionary function is that the standard X30 comes with a 312 MHz processor instead of the 624 MHz on the Axim X51V and other JLT systems (though a few X30s with a 624 MHz processors are available for a few more 円). Dictionary searches thus take about 1.5X as long (processor speed isn't the only issue, which is why it isn't twice as long), but for most searches this is imperceptible--whether a search takes 100 ms or 150 ms, it still seems instant to human eyes and brains. Rarely, searches with many results can take a few seconds--but this isn't common enough for the slower speed of the 324 MHz X30 to be much of a drawback. Of course, if you get the X30 with 624 MHz processor, it's just as fast as the X51V.
The X30 with the Japanese operating system. The OS being Japanese doesn't make much difference if you're just using the dictionary, because you don't need to interact much with the OS for that. As in the other systems, the interface for the dictionary program is in English. If you're only going to use the Axim for the dictionaries, then it makes sense to save a bit of money and get the Japanese OS version. If you might use it for other things, the English version will be easier to use.
The X30 with the English operating system includes the ATOK Japanese input program, which works almost exactly like the Japanese input systems built into the Japanese X30 and the X51V Complete systems. The OS has been slightly customized by JLT to support Japanese fonts and make it compatible with the ATOK Japanese input program (though the difference in price is due solely to the price of the software license for ATOK). ATOK supports both a Japanese/English virtual keyboard and Japanese handwriting entry (you also get the English handwriting entry systems built into the English OS). You can draw an unknown kanji to enter it, just as in all the other JLT systems. Japanese input works the same way as in the other systems, and just as well. Like the Japanese input methods in the other JLT Complete Systems, ATOK's are fully integrated into the OS and work in every program on the Axim.
Included Accessories: 4 GB SD card; JLT documentation, Dell Owner's Manual, and backups on DVD; generic screen protector; stylus; battery, power supply; Dell sync/charge cable; charging adapter; 30 day money back guarantee; 1 year hardware warranty; 3 years support.
As supplies of like-new refurbished X50Vs have largely dried up, I'm no longer offering the X50V system. I'll leave this information up for reference, though.
The PDA itself is externally identical to the X51V, above, but has less memory (the same as the hx4700), and the memory is set up differently (also the same as the hx4700). This means that the user needs to pay some attention when installing new software and copying data (music, videos, maps, whatever) to the PDA to put them on the memory card. It's not hard, though (it's a bit easier with the English version). The Japanese and English versions have very different operating systems, so they're almost like different PDAs. The Japanese version has the same WM2003SE OS as the iPAQ hx4700, above, so all my comments about the hx4700's OS and memory set-up apply to it, as well. The English version has a custom WM6 OS, much like the one on the X51V, and most of the time in use it works pretty much the same way as the X51V. The OS even allows it to use up to 32 GB cards in the SDHC slot, just like the X51V. However, if used intensively, the English X50V can have occasional slowdowns in performance (if you're mostly using the dictionaries and basic built-in programs, though, you may never notice a slowdown--it's mostly power users who will be effected). To minimize these, it's important to keep the main memory as free as possible by keeping as many programs and as much data as possible on a memory card rather than in the main memory of the device. Again, people using just the dictionaries and the basic built-in programs (calendar, contacts, MS office apps, mp3 player) really won't be affected much, and even for power users, the slowdowns are a minor annoyance, not a crippling fault (it seems to be games that are most affected--most other programs use the processor and memory intermittently, allowing the Axim to catch up to itself while you're just looking at the screen and eliminating the need for big slowdowns).
Included Accessories (Japanese version): 4 GB SD card; extra-large 2250 mAH battery with custom battery cover; custom black aluminum case; JLT documentation, Dell Owner's Manual, and backups on DVD; generic screen protector; stylus; power supply; sync/charge cable; 30 day money back guarantee; 1 year hardware warranty; 3 years support.
Included Accessories (Japanese version): 16 GB SDHC card; extra-large 2250 mAH battery with custom battery cover; custom black aluminum case; JLT documentation, Dell Owner's Manual, and backups on DVD; generic screen protector; stylus; power supply; sync/charge cable; 30 day money back guarantee; 1 year hardware warranty; 3 years support.