Thanks much, NHL!
A reason for the overlap in my proposal, is that I'd like to have one workhorse lens for indoor family type pictures (the 17-50 f2.80). and one for outdoors and vacation walk-around and the like(the 28-135) . Of course, I'd often have and use these two together, plus some others (85 f1.8 prime, etc for other uses).
Although I see clear advantages with your approach, am I correct that if I'd like to be able to carry one lens for indoor family pictures, it seems that the 10-22 and 28-135 lenses do not have a good range for those uses?
My thinking is to go with three lenses for family, vacation, etc -- a wide, regular, and extended walk-around zoom lens -- and then add special primes and longer fast zooms for sports, portraits, etc. Not the most economical or convenient, but seems to give me the right tool for the right job, and in some cases, give me a single lens to carry.
If I go that way, I think it would make sense for me to add this very nice Sigma lens that you recommend, or similar Tokina, Sigma, or Canon lenses in this range. In fact, I'd expect to do that. Does this sound ok? What would be your ordering of the following: the competing Sigma(12-24), Canon (10-22), Sigma (10-20), and Tokina (12-24) lenses?