I received the following report about PocketWizards and the 5D Mark III. I have not confirmed this myself.
Been using PW products for 8 years now. I currently have a Canon 1D Mark IV, which works great up to 1/800 at the studio with hyper sync, and preordered a 1D X. I just bought a Canon 5D III and won't sync at shutter speeds higher than 1/160 using Mini TT1 and Paul C. Buff Einstein Flashes fitted with Poceket Wizard Power MC2's. Any speeds higher than that, it will give u the dark band on the bottom of the frame.
I called Tech Support and they say it's not compatible yet and although the 5D III should sync at at least 1/200, the actual speed of the shutter is lower (approx 1/160). They don't even have a test camera yet and they expect the soon-to-be-released 1D X not to be compatible either. They will be working on a firmware update as soon as they have a 5DIII to work with.