The most important thing I think you need to know about this keyboard is that the keys are smaller and closer together than usual. This is because, while keeping to the standard qwerty board size, Logitech have added twelve programmable buttons to the left of the main layout. I thought this would be a stumbling block for me; when I first started using it I was always holding the wrong button down to use a "Ctrl" combination. However, three weeks in I hardly notice the difference, and I'm certainly no great typist.
The keyboard illumination can be switched three different colours, which are also effectively "modes". This simply means that you can program the keys differently each time, say one for flight simulators, one for online etc. For me at least, the pros greatly outweigh the cons. Being a fan of flight simulators, I always seem to run out of keys to bind controls to, so the twelve keys are a great help when the game engine seems to have taken all the "normal" keys up. The keys themselves are comfortable to use with just the right level of resistance.
There is also a built in sound card and usb port which I thought I'd never use, but if I'm listening to music over, say, playing a strategy game, I have found myself controlling the volume with the wheel on the board without having to flick to desktop, so I can hardly complain!
In short then, top notch gaming board that while a little expensive, is in my humble opinion money very well spent.