backlit keys on bluetooth keyboard? say good-bye to good battery life!
Say goodbye to some battery life, but it doesn't need to be very bright (ambient light sensor only activates it when needed - i.e. when its dark, and in that case even small amounts of light will be very obvious). More efficient bluetooth modules could probably make up for it entirely.
An internal battery would be even better. Even at the iPod touch's thickness, Apple can fit in a battery with 36 hours of audio time. In a keyboard, I'd estimate a 4x power saving (pessimistic), or 144 hours (6 continuous days) on a single charge. And that's before you consider auto-off features.