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.
Canon 7D, T3i EOS M, EOS 3, GoPro HD Hero & Hero 2, powershot sx230 hs, Canon 70-200 f2.8 L, Canon 100mm f2.0, Sigma 70mm f2.8 Macro, Canon 50mm f1.8, Canon 22mm f2.0, Sigma 18-50 f2.8, Tokina 11-16 f2.8, Lensbaby Composer, Holga