The new Nouveau driver has vsync enabled by default and it's working great for my two NVIDIA chips: Geforce 210 and another one I don't know the name of. The problem is that in the Shell, tearing occurs even with vsync on. Have tried a lot of NVIDIA drivers and the new nouveau and they clearly decreases the tearing but when watching video in totem or youtube with lots of horizontal motion it's clealy tearing the video playback, especially at the top of the screen.

So I tried a daily build of Ubuntu 13.04 and was stunned by the difference. I can't get any tearing at all in Unity. Video plays flawlessly with nouveau out of the box.

Because I have tried a lot of NVIDIA drivers and the new nouveau in the GNOME Shell (3.4 and 3.6) and I get tearing when watching video but not in Unity, I think this can be some kind of bug in Mutter.

Full screen games and video players like XBMC does not tear in the Shell, but that's probably because theese apps are being unredirected and not compozited by Mutter.

So: GNOME Shell 3.4 / 3.6 tears with nouveau and NVIDIA proprietary drivers but Unity does not.

Tip: It tears even more when watching a video in totem and dragging the window horizontally.

Intel 1.6 GHz (rusty old 2006 CPU)
GeForce 210