Having had a similar experience...
I picked up my first camera in late 2008. I was debating between a Rebel XSI and a 40D. I went with the XSI for budget reasons, but really, I could of picked up the 40D. I didn't have any photography forum to ask questions to and didn't do too much research ahead of time. I just new it had to be Canon as I had some older Canon lenses that I wanted to fit on the camera.
I started taking some classes and getting seriously into photography by the end of that year. By early 2009, I felt that I had already outgrown the camera. I still have it as my main camera, but upgrading when I get back from a trip.
Do I regret the purchase? Well, its a damn nice camera, great to learn, provides great results. What I regret is that I wanted to upgrade soon after. Had I had the 40D, would I of felt the need to upgrade so soon? I Dont know. What I do know is that if I had to do it all over again, I'd get the 40D and then build on lenses.
It all depends on what you plan on doing and how serious you think you will be. The T2i is a good camera, great to learn and grow with. But if you are serious and progress, then you might outgrow it quickly. Maybe you won't.
Either way, focus on the lenses and not the body.
T1i, T2i, 40D, 50D... not a huge difference between them. There is a difference, but again, nothing huge.