Damn there's a lot of hate on for the 85L..
How many of you have actually owned it to try it? from MFD to infinity takes about 2 seconds, yes slow, but look how long the throw is! How often are you going to track a subject from 3 - 25ft in 2 SECONDS?? Real world use is just fine, it's just a challenge to nail focus at f1.2.
I owned the 85 1.8 and wasn't at all impressed by the overall build and image quality.
When I went to upgrade, I considered Sigma's 1.4. I tried it. it was good. for half the price of the Canon, it seemed like a good deal.
However, AF was not accurate in lower light, the build quality seemed cheap, and the image quality/Contrast etc. wasn't as good as the Canon.. Those cons made me choose the Canon, even with the $2k price tag. To me it was worth it..
My point is this:
If it's worth it to me, is it worth it to you? Maybe. Maybe not. I'm sure you can think of tons of better things to do with the ~$1k you'd save by buying the Sigma.
Im not you, you're not me... Make your own decision and be happy with it