Basically the 12 minute limit on the T2i is only for
continuous video. So that means that no single take can be longer than 12 minutes. Is this a problem? Well, that depends on how what kinds of things you'll be shooting with the camera.
If you plan to shoot narrative work, you will almost certainly
never have a take that lasts 12 entire minutes. When I start to notice a long take, I tend to check my watch because I love seeing how far the filmmakers can take it. I'm still impressed when I see a one minute take. I've surely never seen a 12 minute take.
On the other hand, if you plan on shooting documentaries or weddings where you are going to need live, uninterrupted footage and you only have one chance to get it, you will run into problems with the 12 minute limit. Even with as fast as you can hit the record button again, you can miss a lot and you'll get jump cuts.
And to be more specific, in case you were wondering this, the 12 minute rule has nothing to do with how much you can store on a memory card. The amount of footage you can store on a memory card is solely dependent on how big the card is.
As always, if someone knows better than me, please correct
