Do you want to be able to use wide angles with your walkabout lens?
If so, you might find this isnt wide enough, as I did.
I have the 18-135 IS which produces beautiful pictures, but even better are the 17-55 IS and 15-85 IS lenses (and of course they come with a heftier price tag!)
If you dont mind not being able to shoot wide then the 28-135 is good enough as a walkabout, but was really designed for full frame bodies.