I've considered 5870, but at the end got a new MP with the 5870 that's suppose to arrive tomorrow. My old one is going to work for mainly 64 bit windows 2d and 3d CAD work, but I also need OS X on it, and I didn't want to screw around with working-or-not-working card, or any windows only gpu.
Currently, the 30" ACD is running on dual DVI and 23" ACD on MDP to DVI (not dual). I've only had the 23" ACD not light once - but we're talking about 20 or so boots since I got the card - computer sleeps and wakes fine.
My MPs boot rom is MP11.005C.B08
On Wednesday my monitor configuration will change, and I'll probably never get around to using two big displays on that MP. However, on Windows, the card IS better than 8800GT. On OS X....I don't know, and that's because I haven't tried anything serious yet (was getting the windows part going) but
I'll try Starcraft and a bit of Aperture and later on today see how that goes.
On W7x64 at full load the temperature was hovering at around 85-90C with fan running at max RMP when the temp was getting closer to 90C.
adrian