I've only got as far as using C1, almost identical settings to yours but for food and other tripod photography so manual and an aperture of f/4 which I normally use as a starting point. The main thing it helps avoid in my case is picking up the camera later to take a quick shot and getting the dreaded two second beeps while the moment was lost.
That C3 "holy crap" idea is awesome, I can see that coming into use .
No joke on the "dreaded two second delay"... The fact that that will never happen to me again makes me almost want to weep with joy.
usually all the same settings (Av f4) but a range of ISOs so i can quickly flick between them a decent shutter speed. That is the only thing i'd wish for on a new 5d, the ability to set a minimum shutter speed on auto iso, as auto iso goes too slow for me..
Firstly, I completely agree on the minimum shutter speed deal. It is one of my big pet peeves with Canon cameras. I believe that some Nikon cameras have had it for quite a while.
Along those same lines the way the camera meters with an external flash has always bothered me. Anytime I'm using a flash in a dark area (like a birthday party, etc) I usually grab for Manual (M) mode to set the the shutter speed to something that can capture motion (like 1/200 or so) the aperture to wide open and generally ISO 400 or so (depending on how much background I want to pick up vs just the thing lit by the flash). Now that every other option is fixed the camera only has to vary the flash intensity to get the exposure right.
I wish there were a mode that I could set it to that would do something similar automatically. Generally, if I'm shooting in Av mode it will slow the ahutter speed down (and jack the ISO up) as if I didn't have the flash at all...
Finally, two people have now chimed in that they use their Custom modes just for changing ISO! This seems like it might be a design flaw with Canon's camera layout! Personally, I've aleady gotten very fast at mashing the ISO button and dialing in the ISO I want, even without taking my eye away from the camera... but is there some better way of setting ISO?
Maybe a dedicated toggle button? Another dedicated dial? Hmmm....