I am only posting this to second the reviewer who mentioned dirt getting inside this lens. To be sure, this is my travel lens. It is on my 20D 100% of the time. I love the pictures I get from this camera/lens combination; this is definitely the desert island combination for me. I keep it in my Lowe case between shoots, but it gets bumped around and put down in a lot of strange places when I use it. After 8 months in the back of my car and 3 trips including 3 weeks in India, this lens has enough dirt inside that it has to be cleaned. (Any lens that changes volume when you zoom will have a tendency to get dirty inside, but this one seems particularly vulnerable, much more so than my old 28-135 IS that has about the same design and build quality.)
This camera/lens is not my 1DmkII with an L-series prime on it, but this trusty little combo is almost always with me, making it the camera of choice in lots and lots of situations. I have been amazed at how close this little combination will come.