Comment 14 for bug 792315

As Gerry suspected in comment #5, I have the same issue under metacity alone. So it does not seem to be caused by unity-2d itself (at least in my case).
More precisely, here are the results of my tests with different window managers chosen on the login screen :
- Ubuntu (=Unity 3D) : no tearing
- Ubuntu 2D (=Unity-2D) : tearing
- Ubuntu, then running metacity --replace : tearing
- Ubuntu classic : no tearing
- Ubuntu classic (no effects) : tearing