Canon 7D: Canon 15-85 or 17-55 (or third party)

Sorry I can't help you on the 15-85, but I can, with all certainty assure you that the 17-55 2.8 will not disappoint. I've shot two family weddings, numerous car and air displays (where it was the lens of choice over a longer zoom in some situations), and many, many candid and intimate shots too. The only reason I can see for this lens to be deprived of "L" status, is the lack of metal in the barrel(s). Optically, it's up there with the best.