As a console games developer, I currently have a PS2 devkit, Xbox devkit and a GameCube devkit sitting on my desk at work. I use all three daily and I have to say that the GameCube devkit is the most difficult, pain-in-the-arse devkit to use out of all three by a very long margin. I'm not placing any bets on Nintendo making the Revolution devkit very easy to use either.

WILL, perhaps the new GP2X would be a more feasible target for now? It is multiple CPU (dual 200MHz CPUs, to prepare you for when you have to deal with several CPUs on the next-gen consoles), it is based on Linux, and it is all open for people to develop for.