Vsync is not bad in any way when playing games. Only when benchmarking. vSync limits the FPS to the maximum your monitor will allow. So if your refresh rate of your monitor is 70hz, the video card will only render 70 frames per second. This will give you smoother image quality because you will not be missing any of the frames.
This makes it so having vsync off and no fps limit is just like having frame skipp on but rendering the skipped frames. But i guess if you have not fps limit and its running at 170fps, your doing that for a reason.