The first couple years of shooting I only shot manual, as well (back when I shot film). I still shoot manual focus much of the time with my 50L when on the 5D's. Fact is, I do a better job at focusing in many lowlight situations than my 50L does - when most of my other L lenses do it better than I do in those same low light conditions. I would like that to be improved as most L lenses do fine in the same situations - that's all.
Again, it's fine. I'm not saying it's not. I'm not whining. I LOVE my L primes - they're all I shoot with now (haven't picked up my 70-200 2.8 IS in a good while) - but the 50L can DEFINITELY be improved in regard to it's AF. That's all I'm saying. If they improve it, it would be an improvement that would mean something for my personal profession. If they don't, I'm just fine the way it is.
So again, I'm working just fine the way it is - but that doesn't mean I wouldn't welcome the improvement 
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