Just installed my GeForceFX 5800 Ultra on Wednesday. So far, I can run UT2K3 at 1280x1024, 32-bit color, all graphics options set to max and it is more than playable. Yes, that extra fan on there is loud, but it only comes on when you start a program that requires 3D rendering. The ATi 9800 Pro and GeForceFX 5800 Ultra really trade blows back and forth. Each card is better in a specific area than the other. I've always been happy with NVidia cards so that's why I went with it.
As for the loud fan that is on the 5800 Ultra, I saw a "redesign" of the cooling using liquid cooling rather than the small turbo prop you see on small airplanes. It all comes down to brand loyalty now. I suggest you look at what you want your video card to do, and make the best choice. For some reviews, go here:
Tom's Hardware Guide