If they made the autofocus for the 1.4 more reliable and a tad bit sharper at wide open and i'd consider that a major improvement rather than minor improvement. While it's a "fast"lens, it's not fast in terms of the autofocus and I have to almost pace my shooting a bit to let the lens catch up to me before I fire. If I consciously remember to do that, i get a high keeper rate. If I have to shoot at full 8 frames a second with my 7D, i'd be lucky to get any keepers.
I do find on portraits, even on production portraiture (when I shoot daycares, schools, sports teams, etc) 1.4 is way too thin and typically stop down to at most 2.2 or below so that buys me room for error in microfocus and i have an extremely high keeper rate (as long as I pace myself). It would be nice if it could keep up with me for those split second make it or break it shots you get with kids...