I'm also looking for a lens for my Rebel XTi. I didn't have a lenz cap or a UV-Haze on and put a nice gouge right down the middle of the lenz.
The one you're looking at is a bit too posh for my taste. I'm looking for more of a wide angle/general purpose. I already have a 300mm zoom, but from my non digital old rebel 35mm body. It's not the greatest, but for the amount of time I use it it's good enough. I'm considering this one myself
EOS (SLR) EF-S 17-85MM f4-5.6 IS USM also isn't cheap, but I think getting the IS will make the photos much more crisp. For me this will be a general lens for shooting mostly people indoor and outdoor.
From the reviews I've read it's the lens to have as your main one... One day I'll get an IS macro
Just don't feel like dropping a grand right now.