I've used a 7D for a while, mainly for wildlife photography, and I love the camera. A couple weeks back I took the plunge and ordered a 5D Mark iii. It arrived day before yesterday and I immediately mated it with my 100-400 FL 4.5-5.6. I've spent the last two days prowling around and photographing birds.
The differences between this camera and my 7D are simply amazing. The autofocus on the 7D is pretty good. On the Mark iii it is fantastic. I have been able to acquire subjects in lighting that would have been out of the question in the 7D. Noise reduction is far superior in the Mark iii. With my 7D my "go to" ISO is 320. I've been shooting at 640 with the Mark iii and the images are far less noisy than at 320 on my 7D. The metering seems to be superior as well. Spot metered photos with the Mark iii seem to be far less influenced by contrasty backgrounds than with the 7D. Finally, the full frame format is not an apparent disadvantage for shooting wildlife because I can crop my images with much less loss of detail than with the 7D.
This is a wonderful camera and that's based on only two days and couple hundred images' use. I'd thought I'd use my 7D as a backup for the Mark iii but I'm beginning to wonder if I'll ever put the Mark iii down.
Fascinating! Hopefully the 7D MK II has even more improved AF...