The Cell can/might give an edge in terms of more advanced A.I and physics (than the X360 can offer) in some exclusive future games.
In terms of graphics, well the Cell can help a little bit, if you put A LOT of effort trying to musture some graphics capabilites from a CPU. I bet in 2012 we'll see a couple of high-budget Sony-studio-developed games that will do it, but the improvement on the screen will still not be that big of a deal.
Those extra bucks that the Cell cost, Sony should have put into purchasing a better GPU for the PS3. It's really pathetic that a $600 console didn't have a better GPU than the X360 which launched a whole year earlier.
If a programming genius like John Carmack says it's tremendously difficult to run graphics on more than one thread and a game like Alan Wake, which was supposed to take advantage of 4 CPU cores (but in reality uses just two), has taken eons to develop, then it will be a BIG HUGE PAIN to utilize 7 gimped cores for any significant improvement.
