I'm noticing something on my 470, please confirm if it's the same for you:
When I enable VSync or FPS limit on some game, the Usage of the card stays at 100%, but the core freq drops to something between 200 and 500Mhz.
Older cards I've had stayed at top clocks, but usage was 10%, for example.
This one stays at 100% usage, and drops the clock as much as it needs to just make the 60 or whatever FPS I need, and no more.
If I disable VSync, it goes back up to OC clocks.