Necroposting to update. I got the 70D. It's quite a bit nicer than my Rebel in pretty much every way. I wish it were a little lighter though.
With my wide interests, I can't cover everything with a single mode. I can't have a birding mode, a macro mode, a portrait mode, and a landscape mode. In most of those cases though, I have the time beforehand to set things up. And if I don't have that time, then it makes most sense to have the generic "oh crap, get that shot" mode anyway.
I currently have the C mode on exposure bracketing, as I might want to experiment with some light expanded DR work. The more I think about it though, the more I want to do neuro's #2 suggestion. To wit, have the C mode be for situations when you can't take the time to make all the adjustments. However, I wonder if it would be better to select the middle nine AF points instead of just the center.