I very much like backlit keys. My Max Keyboard Blackbird is red, which is just right at its dimmest, although when the side panels reset I always turn them back off.
On the Kinesis Freestyle Edge, I actually like the per-key RGB lighting as well. Most of the alphanumeric and punctuation keys are red, the home keys are green, and the rest are blue. I also turn off the backlight for keys that I don't use, like PRTSC. It looks gaudy as hell, but I feel like it makes it easier to find certain keys in the Freestyle's slightly unusual layout, and to come back to home position.
The other thing I like to do with RGB lighting is to make different layouts different colors--QWERTY is all blue to distinguish it from my multi-color Dvorak.
