I got a GTX 275 a month or so ago and think it's great. I've been using Nvidia cards since my first dedicated beast gaming PC in early 2000s with my 4600. I think it was the 6800 ultra, then the 8800gt, and now the GTX 275. That said, if in 2+ years when I feel the need to upgrade and ATI is the undisputed king, then I will have no problem getting their stuff.
And I'm all for competition and all, but it was getting stupid. Physx is nice and all but it was mostly just a bulletpoint to say "get this over that!" Right now they're doing it again with 3D. ATI kinda pushed ahead with a more practical solution of making a powerful DX11 card.