Go AMD. I've been in the computer business a long time, and I noticed long ago how Intel prices always seemed to drop suddenly for a processor right when a competing AMD processor reached that performance level. Funny how Intel always seemed to find that they could still make money on the CPU at half the cost. Go figure.
We went AMD back in the K6-2 days and have never looked back. As such we missed such Intel wonders as buggy chipsets, Rambus, overpriced CPUs, and missed delivery dates into the channel.
Price / Performance ratio is still with AMD. If you hit the lotto and can afford Intels top $ CPU, you can beat AMD speed by a notch, but I don't think that it is worth it.
I'm quite happy with my Athlon64s thank you - you can get plenty of power for not a lot of $. I'm not convinced that I need to spend the extra bucks on dual core CPUs yet either - there isn't a lot of multihreaded software that can actually do anywhing with a 2nd CPU unless you are running Windows Server.
Don't expect to switch to Vista anytime soon either - it'll be late coming, and my experience with Microsoft is that you don't want to touch any of their operating systems until at least the 3rd bugfix release (SP 2, SE).
EagleDNY
$.02