I have one, it's good, very good in fact but at the moment there are not too many decent games on it.
It really needs to be hooked up to an HD:TV or a computer monitor as the resolution on a standard TV doesn't do the games justice.
The other thing is that the games are very expensive, and with the odd exception the game play is no better than your average PS2 game.
Personally if you are considering breaking the bank for one I wouldn't bother, wait until the other 2 come out (Wii, PS3) and hopefully the 360 should drop in price also, and hopefully there wull be more games for it.