Using a 50mm f1.4 on a 7D will make it an 80mm, BUT how much light do I lose due to the crop factor? Has anyone done this with much success?
1. You don't lose any light
2. Yup, all the time
And the big 3.
What makes you think you need a super fast lens for portraiture? The DOF at 1.4 o 1.2 is mniscule... like the eye in focus, and the eyelashes not in focus.
Classic portraits where you have the eyes and nose both in focus.. you're going to shoot at f/5.6
Intimate portraits... you can shoot however you want for effect, but things go get dicey as far as keepers go when you shoot so close, so wide open, with a (slightly moving) human subject and hand held camera. Very dicey.
As far as oof part of the image is concerned, any outdoor background will be well blurred with 100mm shooting at f/5.6, so no worries there. If you're doing studio portraiture - well, there's a reason all sorts of muslin prints and such were created to give the soft background effect. You'll need a few feet of separation for shadow control anyway, except with the broadest (and most boring) of lighting setups.
If you're tending FF, 100macro gives you dual duty of portraiture and macro
I've always found the 85 too short for portraits, tend to go with 100 for head-n-shoulders and 135 for closer