Yeah on a cropped sensor like the Rebel, a 28-75 wouldn't give you a true wide angle. I suppose you could use it as a walkaround lens but that lack of wide angle would probably be annoying.

I just got the Tamron 17-50/2.8 for Pentax. I like it so far although haven't really shot much with it. Can tell it's optically a pretty nice lens though. Tamron also makes an IS version of the 17-50 for Canon. I can't comment on how effective that is (Pentax has in-body IS).