I have a T2i and use it for video a lot. I love the quality. If you don’t have a canon camera body, and you want to do nice stills and video for the first time, then get a T2i. Firstly, the quality is the same from what I can tell on both cameras. Why? It is because it is the same sensor, just with less processing and throughput. So, why spend more on a camera body when the quality of the recording and stills will not show an effective meaningful difference. If this is your first foray into DSLR nice stills and video then the extra money is much better spent on nicer lenses, memory cards, tripods, and other equipment.
Remember, the camera body takes the picture, yes, but is the lens and you that makes the picture. Which do you think is more important, the camera body, or what lens you use and what you put through that lens for the camera body to capture? The Canon T2i will last you for a long time of learning and use if you don’t know what you’re doing and you don’t have the lens for the job yet.
However, if you all ready have a good lens stock and your much more into photography and video and you have the money, by all means go for the Canon 5D mark 2. What? Why not the 7D? I say the 5D mark 2 because you all ready have a lens setup and you just want to upgrade to a nicer body. In this case it still makes no sense to go with a 7D when for another T2i’s price you can get the 5d mark 2 and get much more advantages in light control and quality with stills and video. So, either way that you look at it from my point of view there is very little need for the 7D. The T2i takes just as sweet videos and the difference in price does not justify almost no difference in function or quality. If you all ready have lens then save the money and get the 5D mark 2 anyway because I am assuming that you are greatly into photography and the only major improvement to your abilities will not be in the 7D over the T2i, but in your lenses and getting the 5d mark 2 over your current digital camera. But even then rumor is that he 5d mark 3 will be out soon from what I hear so, who knows.