So I just got my 5D Mark II today, and beyond the awesome creamyness and detail of the full frame sensor, I didn't realize how much I was missing out with my 60D and it's lack of a micro focus adjustment feature.
Some lenses were just always a bit softer than I thought they should have been on my 60D, but especially my 50 1.8, and 135mm F2.
Come to find out that my 135 was backfocusing about 10 units and my 50 1.8 was front focusing 17 points!
Now the 135 is sharp as heck wide open and the 50 1.8 is finally acceptable at 1.8.
To me, this feature alone is worth investing in, and it's something for Rebel users to think seriously about when looking to upgrade bodies. If you don't want full frame, think about a 50D or 7D.
135 showing back-focus:
Fixed and beautiful!
Thanks for listening.