Ignoring the majority of the photographers (PJ, sports, events/weddings), AF isn't needed.
I happily ignore them!
seriously, I got better shots using my fingers instead of a 'dumb' computer to change the focal plane, AND (and this is crucial, obviously) when I can take the time to do so. But I've found I can _make_ that time, more often than not, and this in itself has already improved my success rate. In the worst case scenario I have to explain to people that my camera is old fashioned, it needs a bit of time. It compels me to try to make ONE killer frame instead of blasting away filling up a CF card. Seriously, I've been having a ball with MF. Plus, less time selecting images in post!
And when the perfect frame is not in focus, I know who to blame... (the subject of course ;-) ) I mean, AF has always given me stress of not being completely sure that it does what I want. Fiddling with the "joystick" (what a eufemism btw!) to select another focus point, etc etc... Sometimes low-tech is better.
But, admittedly, in dark settings especially with the 24-70/2.8, I do need AF to help me out. And then, of course, it lets me down if I want to use one of the outer focus points.