10 out of 10 points and recommendedVery high resolution, excellent feel and construction, very useful optical rangeThe EW-78E lens hood is not included, some Chromatic Aberration at the extremes of the range (15 & 85)
I had the Canon EF-S 17-85mm f/4-5.6 IS USM and liked the flexibility but not the optical quality, too soft some times and a lot of Chromatic Aberration (CA), so I give it to my brother (he's happy with it ;-)).reviewed March 25th, 2010 (purchased for $720)
I bought the Canon EF-S 17-55mm f/2.8 IS USM and this is in other league, excellent resolution, very little CA and you can really use it at f/2.8, so nice but it's heavy and for a walkaround lens the range is limited.
I decided to complement my optics with the Canon EF-S 15-85mm f/3.5-5.6 IS USM and just bought it. So far excellent in all respects mentioned in the Pros. Much much better to the old EF-S 17-85mm.
Even the CA is much less than I expected, I don't know if mine is a golden sample but the CA in the borders of the frame are only important in the extremes of the range 15mm and 85mm, but nothing to worry for normal printing size and for those photos that you care is very easy to fix 100% in Lightroom (I always shoot RAW). Take in to account that my comments are based on the output from a 40D; being "only" 10MP is less demanding than the newer 15MP or 18MP cameras.
Naturally there's some barrel distortion in the wide side (15mm) of the lens, but nothing different to what you get with all this kind of lenses (including the EF-S 17-55mm f/2.8 IS USM).
The IS is great and I feel is even better than the IS in the EF-S 17-55mm f/2.8. I get close to the promised 4 stops.