Dan M , Aug 30, 2010; 05:26 p.m.
Many people have found that one or more of their lenses needed appreciable adjustment, and in that case, MFA is very helpful--saves sending the equipment back to Canon. I have a 50D, which has MFA, but have not used it. All 4 of the lenses I tested were pretty much spot on. Haven't tested my one new one yet. Nonetheless, I would not want to give it up. It's nice insurance.