I've been an AMD fan only up until about a year ago, mainly because a lot of the time Intel's procs weren't as quick as they said they were (for example, you would buy a Centrino 2.8Ghz and it would actually be clocked at 2.53Ghz), but that doesn't seem to happen any more, and they do run a lot cooler and quieter, so if I did do another build, it would be E8400s or Q6600s rather than more Opterons or Phenoms.
It is very unlikely that Apple would move to AMD because of the reason that they run too hot and too loud to fit Apple's smooth, quiet style. I mean, my MBP runs hot enough as it is, with AMDs I would end up with burn marks on my legs xD.