Ken rockwell has reviewed the 85mm 1.2 and 1.8, 100mm f2 and the 135mmf2. I've used all of them except for the 1.2, and i would agree with everything ken says in his reviews. Eventually i sold my 100mmf2 only because i already own a 70-200mm 2.8, and ultimately for me and what i do one stop of speed just wasn't a big enough of a speed advantage over the zoom to justify it(esp considering how fast camera ISO performace is increasing). The IQ from all of these lenses is fantastic. My current best IQ camera is a 5d, and i really can't see a difference between any of these(other than focal length effects, DOF, ect.), or my other lenses like the 70-200, 50mm 1.8, or 300mm2.8 is. I expect that to change with the arrival of my 5dmk3 though.
As for the Sigma, i've had a bad exp with Sigma a couple times, so I really wouldn't even consider anything from them. One time I actually had to wait for 2 months to get an AF problem straightened out. They were literally telling me my part was on a ship, heading to the states, and it would be here next week, then next week, then...(while they had my lens) Besides, i don't see canon offering any lens profiles for them either, so that may or may not be a problem for you.