Picked up 5D3 a couple of days ago. Really liking it. AF fast, accurate, and reliable in single shot mode. Did catch birds in flight in single shot mode, they flew in after testing AFMA with 70-200 and 2x extender. Just happened to have camera in hand. Nailed every shot. Sweet. Started playing around with servo mode. Initial impression with that is it is the improvement I was looking for. Will need to spend more time with it to really get to know what settings to use. HDR is an interesting feature. Can see a few places in my mind already to return to... 100% viewscreen, better display on back, nice feel in hand, shorter shutter lag time. Liveview at ISO 6400 and it didn't look like it was snowing.

Only quibbles are that the AF points don't turn red which is nice to have in low light and that I have yet to find a way to scroll across the top level menus instead of the next level down.

Can't say that any one improvement is jaw-dropping compared to best of 7D and 5D2 which I currently use, but no one has ever accused me of being overly excitable either. It is more a case of starting to believe that I finally have one body that will be able to deliver consistently in landscape, macro, portrait and sports action with enough resolution for me. When I use the 7D on occassion for landscape shots, I do notice the difference. Once the raw processing issues get sorted out, and I test the servo AF more, I expect to be selling 7D and 5D2 bodies to fund a second 5D3 assuming servo passes muster of course.