As far as Java, I agree with the downside on making it more difficult/heavy to install, on the other hand, performance of the JVM is not an issue whatsoever, it was in 2003, nowadays the JVM is VERY fast, pretty close to native code actually and many times faster than any interpreted language.
The UI is not complicated at all, it's layed out so you use the joystick left/right to switch box and up/down to select items. I don't think you could make much more simpler/efficient than that for a joystick driven interface.
Basically the "left" box are filters which you would often set once and leave alone most times, center is "contextual" (lists) and the right is your filtered game list (filtered according to the left/center boxes selection). So often you will just stay in the game list mostly. Also it remembers "state" so if you leave/come back it remembers where you where at so you don't have to go change all that each time.
Well anyway, that's my take on it

I don't think it's cute but it helps me find and select games more quickly than most other frontends ... so if i want to find say all the 2 simultaneous player platform shooter games and/or filter out all the "casino" games it makes that super easy.