Liz,
focus is typical USM -- fast and silent. I've used the 17-55 and the 24-105L lenses and, from the reviews, I expected this lens to be visibly inferior. But it's not. And the color quality is quite nice which most folks don't pay attention to.

As for the 70-200, I've been shooting the 70-200 F2.8L IS for the past week and it's awesome. Here's a shot I took with it on the Florida Circuit last week.



I love it when you can catch them fully-airborne!

Enjoy the 70-200. And I think you'll like the 28-135 a lot.

Jim