I ordered this from B&H the day they started taking orders. I had the 35 1.4 at the time and was looking for a 24 or 20, so this hit the spot. I have never seen anything sharper, like I said it was as sharp as the Sigma 35 and 35 is its weak end, its sharper at 18.
The first copy I got had a focus problem. I would MFA it to my 7D and two days later was way off, after a week of this I sent it back and the new one is great with no focus problems.