I just want to comment on Captainatomic's review posted on 29th December (in the middle of the Christmas break!)
He said "The Sigma 30mm was giving me 1/800th at f1.4 ISO 200 INSIDE!
The Canon was giving me 1/8th at f5.6 (at ~30mm) with IS ON."
Either There was a dramatic light change between the two shots, or the Christmas spirit got the better of him. 1/800 at f1.4 translates to 1/50 at f5.6 Alternatively 1/8 at f5.6 is 1/120 at f1.4. Either way, I think there would have been a fairer comparison, and I would back my 17-85 to at least equal his 30mm in that light.
As noted by many reviewers, 50 to 85mm on a 1.6 camera are great for portraits, but f5.6 is not. That's why I also use 50mm f1.8 and 85mm f1.8 when I'm shooting just portraits outdoors.