This is probably the most boring video on Vimeo but I wanted to show the difference image stabilization makes to camera shake in video footage on the Canon 7D in an utterly unscientific way.
Both shots were at the 55mm end of the lens and involved me doing my best to hold the shot as steady as possible. As you can see the smaller vibrations are removed by the lens stabilization. There is still some movement but the footage is far more watchable (if dull).
I hope this helps anybody else who is undecided about whether to consider a lens with IS.
UPDATED! Now with a few more shots showing pans with the IS on and off. I also did a shot showing how it causes pans to drift at the start and finish when they are on a tripod. Canon recommends that IS is switched off when using a tripod.