Not a fan of IS for video and I see it's use as limited, for several reasons:
The slow shutter benefit is negated by the use of 1/50th or 1/60th at the minimum (1/30th if you ignore the 180 rule)
It's not been designed for video use, and so can be a little aggresive in it's corrections. Video cameras that feature IS (and most serious ones do not) often have a 'soft' is mode.
It becomes less effective the more telephoto you become, video is contiguous, current canon lens IS was not designed for this, in video you are more likely to want to pan or tilt (if you tilt then IS is useless, and can actually interfere with intended video movements) and if you forget to switch it off when you mount the camera on a tripod then you get seasick inducing drifting at 1080p on your nice 50' tv.
I would concentrate on keeping the camera steady, by use of a tripod or a video monopod at the very least (video monopod has a ball and socket foot!) where possible especially with longer focal lengths, other good solutions are things like manfrotto fig-rigs. I'm not a fan of the larger rigs some folks like.
If you shoot video and stills then by all means use the IS for your stills, I just wouldn't bother with it for video at all. If you have a choice of a faster aperture lens vs one with IS, then I would always say, the faster aperture lens.