I also have both on my 5DII, the 85L is the ideal distance, f1.2 is unique bokeh and best for lowlight without flash, colours and contrast are great!
I never tried the 85 1.8, some people say you can't see the difference on a picture, others say it's a big difference. I once asked comparison pictures on different forums but no one wanted to post the demandede same pictures with both lenses @ f1.8 and once f1.2 vs f1.8. So for the moment I keep it, I don't want to buy the 85 1.8L to test and cannot rent it.
First I had the 135L on my 40D, it was too long with the cropfactor, but now on my 5DII it's great, fastest focus, this is one of Canon's best lenses (if not the best). I sold my 200 2.8L to put a 1.4 TC on my 135L cause it's almost the same quality. The only problem (like a lot of people) is that I don't use it so much. I need to use it more, or go out only with this lens 
So 85 1.2L & 135 2L are really complementary lenses.
If a 85 1.2L III would have the same AF speed as the 135L there would be only the 85 1.2L III 






, but I imagine they are slower than dogs, so it shouldn't be an issue (assuming distance is not a problem if you get an accreditation).
