I had a T2i and went to a 7D recently. Got a 17-55 f/2.8 and a 70-200 f/4 L, and I think that's a great combo. Sure, there's a little gap between 55 and 70, but I've never really noticed. Later on, I want to get a 1.4x teleconverter to get more reach. Then eventually upgrade to one of the nicer 70-200 lenses.
I found a great deal on my 70-200 on craigslist. Check around, sometimes deals pop up!