Well mine are driving me crazy right now. Crashes/black screens seem so random. Everything is at stock and I can run through loops of 3Dmark/valley/heaven without a hitch, however loading up Metro (the latest one) crashes out after a few minutes at random places, Star Wars:TOR will play ok for about 15 mins then will black screen for about 2-3 seconds before throwing me back in the game and carrying on as normal (prob display driver recovering after a crash I'm guessing). Strangely BF4 seems fine for the 20 mins or so I tested it, and last but not least is Skyrim which seems quite happy but throws up a nice, multi coloured corrupted screen every now and again for literally a frame and then carries on - if you blink you miss it.
Very frustrated atm. The last ATI cards I owned were 6970's and they never gave me a single issue in crossfire.
Going to try down clocking the ram tonight
Both my cards are Sapphires