I agree with Spak-Spang, $400 dollars is still a lot of money, especially as computer prices keep getting lower and lower. One could probably even buy a budget computer with monitor for around that price. Casual gamers, with possible exeption to the few rich ones, IMO aren't going to drop that much cash for something they won't put a lot of time into. Also, as Microsoft and Sony are attempting to put all kinds of extra features into their systems, the added complexity will turn a lot of people away. The simplicity (hopefully?) of the Revolution should draw crowds of people who are either:
1.) On restricted/real-world budgets
2.) Scared away from the complexity of the other systems.
In addition, b/c you can play NES, SNES and N64 games on Revolution, games which, for the most part, are much more simple (and cheaper), will only serve to reinforce those 2 points.
I see the Xbox 360, (assuming that PS3 retails for 400 and Xbox 360 for 300) being sort of the middle-man in the next iteration of the console wars. With probably? inbetween graphical quality and inbetween price of Revolution and PS3. The fact that Revolution launches so much later than the 360 could even negate the graphical difference between the two.
In my opinion, there are just too many things to go wrong with the PS3 and the Xbox 360 due to all of the crap that their respective companies are/are going to cram in their respective consoles. I'll take a simple system that plays games and dvds with a revolutionary controller, thank you very much.