personally i like the idea of running linux on the xbox hardware as its a 3 normal cpu beast, under linux the cell just looks like 1 of the xbox 360's cpus with a whole lot of coprecessors that need to be specifiaclly programed for (ie its up to the programs not the os to use the cores, you dont write for the cores you dont get the extra cpus)
in some ways i hope sony gets burned on this one, super computers are number crunches not somthing that can make vista run any faster
althogh if you want to do a terminal server farm nothing beats a SSI system running on a super comuputer (makes 200 PCs look like 1 200 CPU machine)