Bought my Canon 35mm f/2.0 IS this afternoon and I like this lens a lot.
Been looking to get back to the 35mm train, had a samyang 35mm 1.4 a while back when it was released but sold it, because wasn't doing that much video and for my shooting at the time MF wasn't cutting it.
When I had the samyang always found myself shooting at f/2.0 and up.
The new Sigma is great and about the same price as the Canon 2.0, but didn't find the need for 1 extra stop of light, a heavier and bigger lens.
My initial thoughts with the Canon, played about 30 minutes with it, expecting to play a bit more on the weekend.
Regarding AF found it fast but slower when close focusing, not that much slower but noticeable.
Found it noisy(similar to the one on the 50mm 1.4) even for USM and this one being a new generation, but became quietter with some use, must have been the sound of the new gears rubbing together.
Focusing ring is very stiff(might get looser with time), not that hard to turn has it was my samyang 85mm, feels good in the hand, could have been a little bigger.
It has a long turn comparing it to the sigma or canon L, but feels nice to have a bit more precision in the MFD.
The Image Stabilizer is great, at this Focal Length isn't very noticeable in the viewfinder that it is on, but for slower shutter speeds is great, I've managed to shoot it without blurring up to 1/5 second. In video found it very usable because you can achieve very steady clips.
In terms of Image stabilizer sound is quieter than the 70-200 II and the 100 L IS.
By the weekend I'll have more time to test and post some samples here.