The newest model in Bandai's WonderSwan line, the SwanCrystal was released on July 12, 2002. It currently has a suggested retail price of ¥7800 (about US$65) although I bought mine for slightly less in Akihabara. It has been released in two colors: Violet Blue and Wine Red.
As someone who owns both a Game Boy Advance and a SwanCrystal, I was fairly unimpressed by the SwanCrystal. The SwanCrystal is notably lighter than the GBA due to the fact that it takes only one AA battery, but the screen (described as "TV-like" by the store saleswoman) is no brighter than the GBA's. The library of games is predominantly RPGs: I picked up Final Fantasy IV in Japanese with the system, and I've been impressed with the game's quality. Most new games will cost about ¥5000 (about US$42) but older and secondhand games are cheaper. The screen resolution is too low to display Kanji clearly, so most games use hiragana and katakana characters instead. The SwanCrystal is fully backward compatible with the WonderSwan Color and WonderSwan, with the advantage over the former being a brighter and larger screen (2.8" versus 2.5").
The accessories market for the SwanCrystal is fairly small: Bandai sells the MobileWonderGate to provide connectivity through a mobile phone, a small robot can be controlled through the serial port, and an adapter provides sound through a standard headphone jack. The lack of a headphone jack on board is annoying, and the sound can only be set to one of four levels: 3 (highest), 2, 1 (lowest), and 0 (off).
The SwanCrystal fits well in the hands, although it takes a little time to get used to the two crosskey buttons on the left side. Each of the X1..X4 and Y1..Y4 buttons operates independently of the others, unlike a d-pad, so diagonal movement is almost too easy. Fortunately, in RPGs this doesn't pose much of a problem. There are no shoulder buttons like with the GBA, but I don't miss them too much.
Neat trick: if you hold down the START button while powering on the SwanCrystal, you can customize the name that is displayed at power-on (it defaults to "SWANCRYSTAL"). Other user data includes date of birth, blood type, and gender. The SwanCrystal does not have a built-in clock to store the current date or time, so it will not be able to wish you Happy Birthday in real time. This data is not lost when batteries are changed.
I'll probably pick up a couple of extra games before leaving Japan, but I would not highly recommend the SwanCrystal to anyone but the most die-hard RPG fans. In any case, it has earned a spot in my video game collection, and FFIV has taught me useful Japanese words like tatakau (attack).