Just as an 85L addict, I share my own experience with the 85L1,2II as one of my two preferred sport lens (with a 300L2,8USM) .. I am using it for a few years with a 1DMKIII, 5DII, 50D and now 1Dx ... AF is definitely accurate and reliable.
That lens needs to be understood and user must be really trained before hoping shooting action. I would say, it's an urban legend that 85L has a defective AF ! it's fast and accurate for any action subjects (users are probably not)

=> DOF can be too small between 90cm and 2m ... I don't think you can get any interesting pictures with one eye or the nose out of focus, so you probably have to close a bit in such short distance range.
=> You have to micro adjust correctly your body not to get any error (I use -3). I even change micro adjustment on the fly depending on the subjects and if eyes are behind an Helmet
=> Action focusing can only be done wide open @f1.2, so users errors are the main difficulties. You have to get trained to be able to keep the right focus point and be able to track one eye, head, helmets for a few seconds (most people are not trained/skilled enough to manage this point).
=> You must be skilled enough to change quickly your focus points and re-frame your subject while shooting.
=> CA can be an issue and must be understood too. For some situations it can be really annoying and it's better to close @f1.8 (CS6 can correct nearly 100% of the CA).
=> AF is as fast as any other L lenses and within 3 meters to infinite. Focusing is near to instant (assuming you are skilled enough to point and shoot correctly !) ... with 1D series you've got more option to give some margin for shooting and tracking with some more users errors margin. Even with apsc like 50D, I get easily more than 80% in focus pictures. With 5DMKII, it's more tricky as DOF is even thinner, but if user is skill-full, AF is really working perfectly too (fast and accurate).
=> 85L1.2II'AF can track any subject without any difficulties at least, I can shoot till 140km/h quadbikes without any errors, I can do even panning @f1.2 (with ND filter).
=> 85L1.2II, 135L2.0 and 300L2.8 can focus and track any subject without hunting, it seems users probably can't . I use more often 85L than 135L because in the night I get more margin for AF.

I have tons of various samples with 85L (I have already put my links quite often on some forums):


=> panning with 85L on fast erratic quadbikes mixing 5DMKII and 1DMKIII http://photos.corbi.eu/photos/swfpop...lbumKey=bc9hkN


=> some dancers in the night with 5DMKII http://photos.corbi.eu/photos/swfpop...lbumKey=BR39X6

=> some fast dogs indoor with 5DMKII http://photos.corbi.eu/photos/swfpop...lbumKey=Hf3kBr

=> quadbikes in the night with 1DMKIII http://photos.corbi.eu/photos/swfpop...lbumKey=ZKGqnT

=> some car race in the night with 1DMKIII http://photos.corbi.eu/photos/swfpop...lbumKey=SdmSFr


Playing near MFD with erratic playing dogs with 5D MKII (I think I got 50% with both eyes in focus, which is not that bad)
http://photos.corbi.eu/photos/swfpop...lbumKey=ZHDFCQ
http://photos.corbi.eu/photos/swfpop...lbumKey=NMvfrr
http://photos.corbi.eu/photos/swfpop...lbumKey=h4KzBQ


tracking capabilities

=> panning shots ith 1DMKIII (some pictures are with ND filters to get a smoothest background as possible) http://photos.corbi.eu/photos/swfpop...lbumKey=bc9hkN

=> Some test of a dog running indoor with 5DMKII http://photos.corbi.eu/photos/swfpop...lbumKey=RFxNqG

=> Some test with dogs running outdoor with 1DMKII (outer focus point used) http://photos.corbi.eu/photos/swfpop...lbumKey=ZrB55t

=> A hundred quadbikes pictures in sequences with 50D (95% were in focused) http://photos.corbi.eu/photos/swfpop...lbumKey=fbJNvC



So in short, 85L1.2II's AF is really accurate and not hunting, assuming users can point and track subjects with F1.2 DOF ! ....

I would say that my 300L2.8 is hunting exactly like my 85L if I miss eyes, head or helmet ...
Such lens is really specific, but there is no difficulty to use it for action/sport.
With 1Dx ... I would say, that I can even shot in a rocking-chair and get 80% of my shots with eyes in the focus.