FWIW, my basic uses/settings are:
C1 - tripod/landscape: Av, f/8, ISO 100, evaluating metering, mirror lock up
C2 - portrait: Av, f/1.2 (so any lens mounted will be set to wide open), ISO 100, spot metering
C3 - BIF aka holy crap what's that?!?: M, 1/1600 s, f/6.3, Auto ISO (on 7D), evaluative metering
I chose those settings for C3 based on a mode dial - it's easy to spin until it stops when in a hurry. I have yet to decide how I'll do that on the 1D X, and I may replace C2 with a low light people shooting setting (Av, auto ISO, min shutter of 1/80 or 1/100 s).