I shoot my 7D at 800 for good shots where I can accept maybe a little motion blur, 1600 where i'd rather have noise than motion blur (noise is easier to get rid of), and 3200 or even higher if it's only going to be a 6x9cm print or 1200x800 web-view.
My EOS 3 I shoot up to 800, which is either BW400CN or TMAX400 pushed a stop, or occasionally when I'm shooting Provia 400 and cross processing, then I set the light-meter to 800 to not blow out the highlights.
And my Pentacon6/Kiev60/Kiev88/Mamiya645AF I shoot Ilford Delta P3200, have shot at 3200 and 4000, and frankly i get better results (less grain than noise) than on my 7D at the same speeds, reducing those huge negatives masks a lot of the grain out. It's hard to compare when my fastest MF lenses are f/2.8, but i'll take my EF 85/1.8 at iso800 on my 7D over the Zeiss Sonnar 180/2.8 at iso3200 on MF (it's also 3kg lighter that way).