I love my Logitech G15. I've had it for about a year now, and it's never let me down. There's also no sign of wear.
Getting used to the key placement was the only thing I wasn't fond of with this keyboard. It took a couple of weeks to realize that the tab, caps lock, and left shift weren't at the very edge of the keyboard - the G keys are. It's sort of like getting used to a new car in a way.
The keyboard has tons of features. As mentioned before, all of the keys are backlit (blue only - I believe the newer Salitek is blue, red, and purple). There's a dimmer switch for the backlighting that has three states - dim, bright, and off. The keyboard also has the usual media keys (play / pause, stop, next track, previous track, volume dial), as well as a mute button. One of the nicest features of the keyboard is a toggle switch that allows you to disable the Windows keys, which is very handy for full-screen gaming.
Finally, the two main features of the keyboard are definately not disappointing. The G keys can be mapped to any normal keystroke (you could set them up as another WASD configuration, for example), as well as macros (full lines of text, excellent for /commands in many games.) The LCD screen isn't something that you're going to stare at all the time, but it is nice for at-a-glance stats, or seeing the time if you don't have a clock in the room. In most of the supported games, it'll give you information about your ammo, level, location, etc. One of the handiest things is the Ventrilo support, which will show you who's keyed-up, which channel you're in, and a few other things even during a full-screen game.
Overall, the keyboard was one of my best purchases. It's very pricey compared to other keyboards, but the features are definately worth the extra cash.