I upgraded from a 60D to 5D3 a year ago for two main reasons...High ISO capabilities for low light, no flash work, and absolute drop-dead sharp focusing...which took me a while to get used to. The extra quiet shutter mode is a nice 'freebie' as well, since I do a lot of my photography at non-wedding church events. Reason #4...the ability to MFA my lenses. Although none of my lenses were out by more than + or - 5, the improvement was noticeable, especially when pixel peeping. Being able to MFA each end of the zoom lens ranges surprised me, as I figured they'd be the same. My only sort-of complaints about the 5D3 is the loss of the swivel screen and the somewhat unexpected size & weight differential compared to the 60D. As for IQ, I had no complaints with the 60D. My only issue was noise at ISO 3200 and up. Shooting with all L lenses on the 60D has the advantage of using only the center area of the projected images from the lens...less distortion, CA, etc. I -did- notice, however, my 16-35 f2.8L gets a lot less use with the 5D3 than the 60D as the 24mm end of the 24-105 is 'wide enough' on the 5D3, where as I needed the 16mm end of the 16-35 to get an FOV of a theoretical 25mm lens. The first shot was with my 60D - 24-105 f4L at 70mm, f4, 1/100, ISO 1600. <img src="http://www.thephotoforum.com/forum/attachment.php?attachmentid=60916"/> This one's with the 5D3, same 24-105 f4L at 105mm, f4, ISO 3200, 1/40th <img src="http://www.thephotoforum.com/forum/attachment.php?attachmentid=60917"/> And lastly, 5D3 with 135 f2L wide open (what else?), ISO 3200 at 1/320 <img src="http://www.thephotoforum.com/forum/attachment.php?attachmentid=60918"/> I am more than satisfied with what I can do with the 5D3 that the 60D couldn't. Now all I have to do is finish paying off the credit cards!