I had a Canon 17-85mm. The IS, USM and zoom range are great and the only optical downside that I found to be significant was the distortion at the 17mm end which was only just possible to correct with my correction software doing its very best and working very hard. I'm sure that I read a review that said that this lens distorted more than any similar lens they'd ever tested. Apart from that mine was ok.
However, I replaced mine with a Tamron 17-50mm (non IS) which I personally think is a much better lens although it lacks IS and USM and doesn't have the same zoom range. It does however have f2.8 available throughout it's zoom range and it's quite a compact lens.
There's a very similar Sigma 18-50mm f2.8 and both the Tamron and the Sigma are now available with IS, the Sigma has HSM too. There's also the Canon 17-55mm IS USM which some say has the best image quality, but it's also bigger and more money.
PS. I'm sure you get a hood with the Tamron and Sigma lenses, with the Canon you have to buy one.