If you can only get one, I'd get the 15-85.
I love how this guys set out very specific guidelines to what he needed/wanted and everyone pretty much did not follow them whatsoever...
While the Canon EF-S 15-85mm f/3.5-5.6 IS USM Lens and the Canon EF-S 17-85mm f/4-5.6 IS USM Lens seem similar in specs and even appearance, the 15-85 is a significant upgrade in image quality.
The 17-85 is still a decent lens. But, I highly recommend the Canon EF-S 15-85mm f/3.5-5.6 IS USM Lens over the 17-85.
neuroanatomist said:Interestingly, no one has suggested 3rd party lenses. I haven't used one, but reportedly the Tamron 17-50mm f/2.8 non-VC is an excellent lens (optically better than the VC version). AF is supposedly loud and a bit slow, but it's otherwise a great value - fast aperture (for a zoom), good general purpose focal length on a crop body, and the price is right...