Upload & Sell: Off
Well, with many cameras people change the focusing screens so that they can accurately manual focus fast lenses and are quite happy afterwards. If you want to only AF, that's fine, your preference and some folks don't have a choice. Some activities like sports and fast moving subjects, no question you're going to get a lot more keepers using a properly set up AF camera. Or if you have poor vision or it's failing.
I'm sort of amused that you haven't heard of focusing issues with the 50L though. When I shot Canon, and frequented a Canon forum, there was widespread and worldwide wailing about focusing issues with Canon in general and the 50L in particular. I had the 24L, 50L, 70-200L, 85 1.8, and a bunch of other glass, and I fine tuned it properly, and I still got so many misses on shots I really would have liked to have been keepers. My Canons focused very fast and very unreliably. Many unhappy users on the forums told similar stories, or how the 5DII was so great but only the center point actually worked reliably, or how you had to buy 1D series to get real AF.
I switched to Nikon and with the same techniques it was a whole 'nother world of accuracy - pretty much any misses I felt were my fault, so I got to work on improving technique instead of wondering whether buying a full pro body would finally get me reliable AF.
It sounds like Canon has improved their game with the latest round of bodies, which is great. But not in time to avoid losing this customer.