Just picked up a new 5D3 last week and took it out for a little high school volleyball over the weekend at the Kentucky High School State Championship. Overall very pleased with the AF, as I had very little time to experiment before putting it into use.
The best surprise, however, has been how clean the images were. I'd shot my daughter's high school team with a 1D2 the past couple of season and shooting at ISO 1600, I'd be lucky to get a SS of 1/500 with my 135MM F2. Given a brand new high school gym this weekend with fantastic lighting, I shot most of the weekend around ISO 5000, SS of 1/1600, with my 70-200MM F2.8.
These are SOOC JPG's with no post processing. I shot the same images in RAW and haven't had time to mess with them yet.