Vsync's mandatory on all games for me. With triple buffering, there's no performance penalty and 60fps is more than enough. Plus, with all the pc games originally being designed for consoles, my GTX260 has monstrous power (compared to consoles) and maintaining a constant 60fps isn't an issue in 90% of modern games.
Vsync for life. I'd prefer a game that is at 60fps constantly rather than running at 150fps but dipping down to 70-80 fps during heavy action. The drop is noticeable, even if it's still running very fast. 60fps constant, on the otherhand, is silky smooth throughout. But it's the lack of screen tearing that makes me such a fan of vsync, it looks so much nicer with vsync enabled.