I recently picked up the vanilla (non-SC) version of this card and have run 3DMark Vantage without problems and I'm working my way through a stack of games I had been collecting, waiting for this upgrade. It's been great with no glitches or nvidia crashes even during multi-hour play sessions. I was afraid it might overheat, because it's a tight fit in my SFF case, but I haven't had any problems at all.
My card is still at stock since I don't have any game that I can't run at 1650x1080 with AA/AF cranked. I'm very happy with this card, especially since I skipped a few generations of upgrades.
It definitely sounds like you got a bad pick. I've had good luck with mine and would definitely recommend a straight replacement (or just exchange for a vanilla). You could also wait a bit for the GTX 275 if you can get a refund.