I have both the 17-55 f2.8 and the 15-85 lenses. The constant 2.8f is nice if you are taking portraits or working in low light and your subject is close. however, i personally like to shoot photos with a long depth of field, so i rarely use a low f anyways. What you want is a good general purpose lens for no more than $1000; the 15-85mm is that lens.


If you always want a nice blurred background (which i honestly don't care that much about) and will be doing a lot of portrait work, than get the 17-55 f2.8. It has better glass andbuild as well. Otherwise, save some money and get the 15-85; it is much better than your kit lens and the extra reach comes in handy a lot.