Lens works fine, there are no problems with autofocus (bf & ff), picture quality is very good and VC works great (it's silent and this is very important when you're recording videos).
UPDATE (after 6 months)
Lens is in good condition, but it has dust inside. In the meantime I bought Canon 70-200/2.8 IS II, so now better option for me is 16-35/4 IS.
Pros:
- very good image quality from 4.0-11 (at 2.8 very good on 24 mm)
- VC is silent and effective (3 EV);
- price
- af works fine
- af works fine
Cons:
- high vignetting;
- distortion at 24 mm;
- AF is slow in low-light conditions (but it's still ok)
- flares & glare
- no weather sealed
- flares & glare
- no weather sealed
Aperture - f/11.0; shutter speed - 25s; iso 100; focal length - 24 mm (cropped)
Aperture - f/11.0; shutter speed - 30s; iso 160; focal length - 42 mm
Aperture - f/8.0; shutter speed - 30s; iso 200; focal length - 38 mm
Aperture - f/6.3; shutter speed - 30s; iso 100; focal length - 33 mm
Aperture - f/6.3; shutter speed - 1/160; iso 50; focal length - 63 mm
Aperture - f/4.5; shutter speed - 1/50; iso 2000; focal length - 24 mm
Aperture - f/10.0; shutter speed - 30s; iso 50; focal length - 36 mm
Aperture - f/5.6; shutter speed - 10s; iso 50; focal length - 70 mm
Aperture - f/4.0; shutter speed - 1/100; iso 5000; focal length - 24 mm
Aperture - f/5.0; shutter speed - 1/250; iso 3200; focal length - 53 mm
Aperture - f/3.5; shutter speed - 1/500; iso 2500; focal length - 50 mm
Aperture - f/5.6; shutter speed - 1/160; iso 200; focal length - 51 mm (cropped)
Sample video (aperture at f8, focal length 70 mm, iso 6400, ALL-I, post process in Pinnacle Studio):