Well I shoot a little bit of everything (not very helpful I know). Probably landscapes, and people mostly. Situations where I'd need the nicer autofocus don't happen too often, but when they do, it'd be nice to have better autofocus than I'm used to in my T1i.
Another reason for the 24-70 is because it can focus so closely I might be able to convince myself that I don't need a macro down the road
The 16-35/5D III combo would be pretty nice, but probably too wide to hold me over while I saved up for another good zoom. Plus I'm sure 24mm is more than wide enough for my tastes on full frame. And the 24-105 is another possibility, but that 2.8 aperture is really appealing for the shallower DOF