Just my 2 cents...
I honestly believe the Canon 5D Mark III was rushed out the door in attempt to steal some thunder from Nikon's mighty 36MP D800. Yes it may have been already in the production pipeline but I believe it wasn't quite ready for public release.
I use the fact that 1DX being delayed by several months as a prime example. The 1DX was announced way before the 5D Mark III and yet Canon's engineers have determined it isn't quite ready yet. There are obviously problems that still plague their flagship release. The same can be assumed of the 5D Mark III which was rushed out the door just after being announced, I assume in attempt to stop a lot of photographers from jumping ship to Nikon.
After using the 5D Mark III in different real world shooting scenarios (tests and charts can be misleading), I can say that this camera does NOT perform up to expectations.
Yes it has great resolution and should provide an excellent advantage to landscape and still life photographers, but it's advertised performance over previous models is questionable. After shooting Steph Pockets (who by the way gave an excellent performance last night), I was very disappointed with the results. The camera was not able to lock focus most of the time. Granted it was a very dark night club with next to nil for lighting, but I shot many times before in similar conditions with my trusty 1D Mark IV and came back with a much higher percentage of usable shots.
The 5D Mark III seems to work well in a studio environment where the subject and lighting can be controlled (even then, I would question the focusing system as it seems to be a little soft). I would not recommend this camera in it's present state for event photography and I'm seriously considering returning mine. I think Canon needs to work on perfecting the AF with firmware updates.
I will say that the ISO performance was very good and the noise levels were unexpectedly low. My biggest gripe with this camera is the soft focusing AF. I want and expect my images to be tack sharp for a camera at this price point and marketed to professionals.