I feel like there must be something way wrong with the way vsync is implemented in most games. It often feels like it adds massive latency (like an entire extra buffered frame, like bad implementations of triple buffering), but if my FPS is close to what it would be with vsync, then I don't see why it should add much latency.

That is to say, on my 60Hz monitor, I don't feel much difference between 60 FPS and anything above with vsync off. But if I go from from 70FPS (vsync off) to 60 FPS (vsync on), it's yarrgh unplayable, as far as first person shooters go.