I have two 560Ti Classy's currently running at 880/2100 @ 1.050. I've played BF3, Metro 2033, Crysis, Mafia 2...all with no problems. I was running it at 1.038 and it go through OC Scanner 20 minute stress test and two hour BF3 session with no problems, but froze during a 3DMark11 run so I bumped them to 1.050.
My 3DMark11 Score was: 11305
Overall I absolutely love these cards. They look great and perform even better. I plan to keep bumping them up to see as far as they can go but I need to replace my UPS. It's starting to reach it limits and when I run the cards hard it sometimes causes the warning alarm to sound and shut down my rig
Nothing a quick trip to Microcenter won't fix.