I've not used auto-focus, but personally I don't like technology if it is mandatory for the operation of something that can be done mechanically. I want things that are robust enough to function even if the electronics die. Unfortunately, my main/favorite camera is a Sears KS-2 (Ricoh XR-7), with coupled meter and battery. Not much to go wrong, but enough to make me worry.
In general, if a manual mode is achieved by an electronic switch, and the electronics die, then it can't be used manually.
If manual mode is purely a mechanical option, there I'm fine with the automatic functions, since I can still use the device if the automatic part breaks.
A smart phone is basically a computer, and I don't like how it's camera focuses and decides what the light level should be. I'd not have the patience to deal with things like that in a real camera, digital or otherwise.
I can see situations where auto-focus would be very useful, but I'm not in those situations. Manual is fine for the photos I want, and if I wanted convenient or easy, I'd pay someone to do it for me.