I sold 135L due to inflexibility and arranged with this seller to buy his Canon 70-200 2.8 MK II, but someone else bought it before me. Out of frustration I bought the sigma 70-200 f/2.8 HSM (the first generation, no DG, no macro) for cheap $450 for temporary use. Turned out that I love this lens : quick AF, great color and PQ. After a weeks' use I realized occasionally I still need f/2 lens for freezing action , then I got the 100mm f/2 lens for $400, which is very similar to the 85 f/1.8 lens (two copies) I owned before.
I was under the impression that the sigma zoom wide open has similar PQ to the 85 f/1.8 wide open (I know the apertures are different). Out of the curiosity today I did a quick , very unscientific comparison.
The siggy looks really good against the prime. For those who want a fast 70-200 2.8 but on a budget, this might be worth considering.
Canon 100mm @ f2, ISO 640, 1/250 sec
Siggy 97mm @ f2.8, ISO 640, 1/100 sec
Canon 100% crop
Siggy 100% crop