Thank you to everyone, sincerely.

I used all of your sound advice and thought about how the lens would 'fit' in my bag and decided to go with the 17-55. Since I already have the Canon 100mm F/2.8 and the 70-200 F/2.8 (well, I'll have it Friday) I decided on the faster lens instead of the extra reach. Again, thanks to everyone for your great advice!