I bought this to compliment my 135 F2, sadly the image stabilizer ( which was wisper quiet & didn't make a clunking noise when switched on) actually seemed to introduce blur on shots between 125th - 320th! I tried it on 2 Canon 5D mk3 bodies, both showed problems. I would also get errattic focus on still subjects even at 3m in good light with apertures of f2.8/4. I get no problems with my 70-200 IS.
I bought this for portraiture, shooting at 3m, often f2 @ 160th. I found i got more keepers with my 135 f2 at a metre further back and a very similar aesthetic. I'd recommend the 135 F2 if you have space, or a 70-200 IS instead of this lens. I also have the 35 F1.4 mk2 which is stunning for accuracy and quality and much more versatile than I though it would be.
When it hit focus, in bright light, it was very impressive but was let down by focus inconsistency and the introduction of an odd circular blur that occurred on every other frame of a sequence I shot. I probably got a dud, others love this lens but I felt uneasy relying on it, so I returned it.