As you are buying a top-of-the-line APS-C type camera, it makes sense to get the best lens for it. I wouldn't get the EF-S 17-85 IS if optical quality is your highest consideration. Optically, there is little to choose between the remaining candidates. Check out the reviews on this site and others.


I own the EF-S 17-55 IS f/2.8 and the EF 24-105 L IS f/4. They are both great lenses, although I use the 17-55 more on my 40D because:


1. It's faster.


2. It's a better fit range-wise from wide to moderate zoom for my needs on a APS-C sized sensor.


3. It's lighter, and that makes a difference on camera you carry all day.


I've considered buying the 24-70mm f/2.8 in the past and am considering it more these days now that I have a full-frame 5D II but I'm holding off as I don't need it immediately and I suspect a 24-70mm IS version is not too far down the pipeline. For me, IS is very important. If I'm not using a tripod, I will shake!