v-sync, synchronizes your cards frame rate to the refresh rate of your monitor.
The only real reason to turn it off, is for benchmarking where you want a measure of the raw speed of the card.
If you turn it off, your frame rate may well jump above your monitor refresh rate (only if its maxed when vsync is on). BUT if your monitor is running 85hz, no matter how much of a frame rate jump you get... you are only seeing 85 frames per second.
Correct me if i'm wrong anyone..
SKurj
