Wait for vertical sync?

I noticed this in the graphics options a long time ago, but what benefit does it give for having it on?

It deals with the fps of the video card and monitor.

If you have a hefty system, leave it checked.

vertical sync will stop horizontal tiling.

In games you may notice when you move around you have horizontal lines going across the screen.

your fps may go down with it on but you stop the tiling.

It limits your maximum frame rate to match the refresh rate of the monitor. I prefer unchecking it.

It's really only helpful on high end systems as on low end systems, it can actually start cutting your fps in half.