The changes noted by Anzwix for the Mir trunk code are:
Rev 511 - Mir now supports multi-threaded compositing where there is one thread per output frame-buffer (DisplayBuffer).
Rev 516 - The rest of the functions have been hooked up to enable on Mir a fully synchronous client API. Mir is namely designed to be a asynchronous while for those wanting to write a simple synchronous program for Mir, the option is out there. This commit also makes all but one of the example Mir clients synchronous.
The recent Mir activity will be further looked at in the morning. There's also other branches of Mir code by Mir's small development team for those wanting to explore other features being baked for this Wayland competitor.