I'll be the intel guy....I run dual 2.6 xeons
Disclaimer: I don't game, do mainly graphics/cad/3d work, and generally multitask amongst 5-6 such programs all the time.
Price/performance at most levels except the ultra high end (opteron 265-275), for what I do, intel has had for the past year and a half or so (built system almost a year ago)
the introduction of single socket, dual core chips from both AMD and intel has made or will shortly make such a distinction nearly impossible. Right now it looks like intel dual core will be a godsend for budget workstation builders, AMD X2 is a great thing for those with slightly more cash, and dual core opterons taking up the high end. current xeons probably don't have much of a niche except maybe a pretty narrow band between the X2 and the 265 or 270, depending on the application.
And who knows how this will change as prices settle and the dempsey dual core xeons come out next year
next upgrade will be between socket F opterons and dempsey xeons, whoever has the best price/performance at the time