I made the switch in both the new rig and the old one. In the old replaced the BFG 9800GTX+ with a XFX HD4890, and I couldn't be happier. GTA4 actually runs very well on it now, on a dual core rig which I never thought possible.
As far as the new rig, I'm AMD all the way, but have always preffered Nvidia Gpu's. Well as of right now, NO. I went AMD/ATI all the way and I'm perfectly happy, there's no game or app I can't blaze through.
And for that ignorant comment on page 1, about comparing x to y when overclocking, and how stupid it is, it's called "PRICE". For the PRICE of a 5870 I got TWO XFX 4890's, put a 100mhz OC on the core of both of them (because they did this on TomsHardware.com and got a single 4890 to beat a GTX 285) and I'm perfectly happy now. I have my Cpu overclocked like mad and it's stable and cool and happy, and sick fast, more than enough to keep up to the Gpu's.
This thread turned in to a bunch of bs...I only wanted a few opinions. Well, I don't need them if people are going to act this way, besides, the proof is in the performance I get right now, which makes liars out of half the people in this thread.