But default to double buffering still, until all backends support it.
If you want to try it out, just change the constant in clutter_stage_view_constructed from 2 to 3. But it only works on Xorg right now. For me the most noticeable improvement is that I can suddenly scroll the icon grid at 60Hz, while using master it's 30Hz.
Prerequisites (included here): !1381 (closed), !1382 (closed)