I've always liked AMD, so take all this with a helping of salt.
My last two chipsets were AMD, both Gigabyte boards; these were both incredible. The stability, versatility and raw power I got was a lot of fun. With the last box, I got my first quad core. Coming from a dual core and working with CPU intensive problems (CFD, FEM and CAD, with meshing code written in Matlab), the quad core was an incredible experience. With the quad core, I also switched back to and ATI card, the 5850. The card is still running strong, with very little signs of aging; I'm guessing I'll only have to upgrade when the 8xxx series comes out! My next box will definitely be an AMD board and card combo.
My fanboyism comes from my great experience with AMD products, and Intel fanboys can try their hardest to convince me otherwise, but they won't.