For stills the differences are bigger, but if someone is just shooting video you'd be hard pressed to tell the differences between the T3i/60D/7D.
I disagree on the video side of things. The flip out screens of the T3i & 60D, the manual audio levels of the T3i & 60D and the Magic Lantern compatability make the 7D the weakest choice for video.
Intermediate ISO and live hdmi output aren't enough of a benefit, IF you are buying purely on a video basis.
Depending on your stills interests then the arguements for the 7D may well be more compelling. I say this as an owner of both the 7D and the T3i, and a serious video user.