I get the same. 3570k, AMD 7950 HD - annoying stutter with "sync game to audio", with any combinations of settings including disabling audio. Same results with either a sound card (X-fi using OpenAL) or onboard (DS or XAudio2). DPC latency checker reveals less than 100 microseconds latency at all times (usually around 40). I can replicate this in all the machines in my house. Afterburner's 2.3.0 fps counter that updates many times a second never dips below 60fps, yet the visuals stutter.
IDK if it's because I'm highly sensitive to frame dropping or not but I assume there are others out there with the same problem. Could you please take another look at this/suggest a fix? Without sync game to audio I get fps problems - the games run about 5fps too fast, and it's noticeable.
P.S Regarding frame buffers, is there a reason why 2 frames is the minimum? I don't have anyone to help me A/B but Rhythm heaven feels pretty different depending on what the buffer is set to. Not complaining, just curious.