Just to throw a cat amongst the pigeons here.
it's worth taking a look at some of the "jail-break" developments taking place for the T2i/550D
what is being developed really puts the the 550D out near the front with cameras like the 5d Mk II
anyway have a look at this:-
http://vimeo.com/17786851
Just what I was about to say! As already stated they are developing for 60D but it is not there yet...
The 4K thing was a rather uninventive excuse to Rick Roll us btw. (although the people behind magic lantern thought it could be possible....)
Anyway to restate what others have said - GLASS
I got a 550D as I wanted the hack asap.
(I use a Sanyo Xacti HD2000 when I shoot anything that would really require a moveable screen or without aliasing/moire.)
550D I go with view finder and money on Lenses -
I got -
Tokina 11-16 (cost as much as the camera near enough)
Second Hand Sigma 28mm f1.4
Canon 50mm f1.8
Then Various filters, polarising, Neutral Density etc.
Also accessories like an Intervalometer for time lapse, cheap shoulder rig, LED light (made one), some big 4 way reflector/diffusers and an external audio recorder (already had one) all push the price up.
I easily tripled the price of the body on all of the extras so if you can afford to do something along those lines and get the 60D it is worth it... but the 550D will do you proud if you can live without the swivel screen.