My wife and I shot a wedding yesterday, we brought two 5DII bodies, and one 5DIII body. I didn't bring out the 5DIII until the reception because I didn't want to use it for the critical stuff until I've spent more time with it. For the reception ( private room inside restaurant ) we were using the 85 f/1.2L II, 35 f/1.5L and 50 f/1.4. I lost many good shots because the 5DIII took 2-3 seconds to focus. I tested focusing in the low light with all the lenses, and the results were similar ( well, the 85 was even slower, because that lens is just slow focusing ). For AF, I had "one shot" selected, and the center point with the 4 surrounding points. I couldn't easily do a side by side because I didn't have two of any one lens, but I did switch lenses between the bodies and played around some. The 5DIII was as slow, or possibly even slower than the 5DII to achieve focus. The amout of natural light in the reception was around ISO1600, f/1.4 and 1/60. Oh, and I had a flash on, putting out that red focus assist as well during all this testing! Anyway, just giving people a heads up on what I experienced, and I've seen some others post the same. I've also seen people post results of miraculous AF improvement with the 5DIII...