I had this lens a long time ago, I forgot how 'unsharp' it would be at f2.8, it can vary from copy to copy, just saw a youtube video but it isn't so bad at all, with a bit of extra sharpening in pp.
For this lens I sold my Tamron 24-70 2.8 VC as I didn't like the backward zoom.
I doubted till the last minute to rebuy the 35 Art, but as I had the 50 Art allready I opted for the zoom.
We'll see if I like it again, if not I sell it and go back to the 35 Art...
Just noticed Tokina made (again) perfect optics with their 24-70 2.8, a pity their AF motor is still not excellent fast next to their perfect glass...
http://www.kenrockwell.com/tokina/24-70mm-f28.htm