I have the Tamron 17-50 and my biggest problem with it is the focal range. This lens is my walkaround lens, and it is on my camera almost exclusively. When I get frustrated it's not because the lens doesn't get as wide as I want, but rather because the lens doesn't get as long as I want.
I'm a big fan of the 17-50, but I really think that you need to consider what you will lose.
60D, EF-S 10-22mm f/3.5-4.5, EF-S 18-135mm 3.5-5.6 IS, EF-S 55-250mm f/4-5.6 IS, Tamron 17-50mm f/2.8, EF 28mm f/1.8, EF 50mm f/1.8, EF-S 60mm f/2.8 macro, EF 85mm f/1.8, 430ex, 220ex, Alien Bee B400 (2), Alien Bee B800 (2)