550D worth getting?
I have a T2i and it's awesome. If you can afford the 7D go for it, I'm a proponent of buying the best you can afford BUT, with a DSLR the lens you use is equally important I would say. So if you bought a 7D with a kit lens versus a T2i with an L-Series lens, at the end of the day I would say you would get better pictures with the T2i because you have a better lens.
Plus, Magic Lantern works with the 550 and doesn't yet for the 7D. Magic lantern is pretty amazing.
Tough decision but either way you end up with a great camera. Grats!