I hear the 18-55IS is pretty good as kit lenses go. It doesn't seem as bad as the old non-IS kit lens but I've never used either personally. I have the 17-85IS and from the one time I've used it in anger it seems OK.
I guess the 17-85IS does everything the 18-55IS does and then a little more so the 17-85 seems like a safe bet if the extra money isn't a problem.