As far as what you will get with the 7d over the t2i from a video based standpoint, there are a decent amount of differences. Those saying the two are similar are completely off base.
The 7d's ISO sensitivity is amazing compared to the t2i. While a DSLR is already on par with high end video cameras in light sensitivity, the 7d is the king of the night, rivaled only by the upcoming 1d mk4.
Also, the 7d's settings are much easier to access with many more having dedicated buttons, vs. the t2i's horrible menu interface. I played with a t2i in the store a few times to verify that I had made the right choice, and there is no comparison. The 7d is awesome.
As if that wasn't enough, the build quality on both bodies is leaps and bounds apart. The 7d when I first got it astounded be by how solid it felt. Is it a little heavy to tour with? Yea, but knowing that I can get rained on and it will still work is a comforting feeling. The t2i is not weather sealed and feels pretty chintzy.
Lastly, the 7d is super accepting of whatever you want to throw on it. I dont know what the t2i will do, but chucking a Nikon manual prime on a 7d with only an adapter will still let you shoot auto and 8fps. You just need to set your desired aperture, focus, and then fire away. I don't know how the t2i would react. The 7d reacts wonderfully though.
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