Last week I upgraded to an Athlon64 + Asus k8v combo.
The installation went without a hitch, stability has been good and speed, well, it simply blows away my earlier XP1900+.
In americasarmy my framerates went from mid 20's to 85 (vsync.)
It was a good purchase.
I even installed 64-bit XP on it.. As any XP it sucks bollocks though. It has even more 'helpful' automated functions that do nothing but enrage the end-user.
For example: Try to configure a network connection. Use add-wizard. It says 'network connection SHOULD already be configured.' But it isn't as the gigabit-lan drivers aren't compatible.
Gotta love it.