My EVGA 8800GT SSC is a crap card. Its the fastest GT EVGA released, but with the original smaller fan that makes a very loud whine when it speeds up. And yes, it is as unstable as you've heard; I never overclocked it, yet in some games I'd get artifacts, lockups, crashes, etc. EVGA released a new BIOS that sped up the fan under load, but that was a mixed blessing since the fan was just f@cking annoying.
Judging by all the posts in EVGA's forum, my card is typical of their factory-OCed GTs; GPU pushed way too far with insufficient cooling, RAM right on the edge of unstable, and apparently no QC whatsoever (and I like EVGA, by the way).
So I replaced it with an EVGA 8800GTS 512, which is much better in every way. Faster, quieter, cooler, and infinitely more stable and overclockable. If you're planning to buy, get the GTS 512 and don't even waste your time with the GT.