I don't see how programming for the Cell is going to be different than coding for the PowerPC - for the programmer it doesn't really matter how many cores there are above one.
Programming the XBox and XBox 360 is essentially the same as programming a PC.
That's not what I've heard from the people I know who develop for them, but I can't really comment personally since I've only ever worked on Amiga and N64 games on any significant scale, and that was at least 10 years ago, so I'm sure it's not particularly relevant any more.