New 70-200/2.8L IS "clicks" ... problem?

My new lens (70-200/2.8L IS USM) makes a very audible "click" noise when it snaps into focus each time. The drive itself is silent, but it sounds more like things are crashing into alignment rather than gliding into alignment.

This is the first example of the lens I've ever handled, so I don't know whether this is (a) normal, (b) abnormal but nothing to worry about, or (c) holy leaping lenses Batman return that lens before it's too late!

Advice welcomed ...

Try turning off the IS. On my lens the IS kicks in with a little "click" when shutterbutton is depressed half-way, followed by a little buzz. This is totally normal.