The T2i is pretty aggressive with in-camera NR for jpegs. And it's a pretty good NR. But it's kinda deceptive when comparing it to other cameras, especially those that did not have any jpeg in-camera NR. (Such as the XTi). The OOC jpegs look fantastic from the T2i, but at closer inspection it's obvious that subtle detail is wiped out by ths NR at higher ISO's, which is OK because a high ISO image quality is always some sort of compromise between detail and noise. If you want low noise and great detail preservation, get a D3s (or a 5dII) But seriously, the jpegs look great from the T2i thanks to a pretty good NR system.
I think the T2i is a great body, I owned a 40D and loved it, but I don't doubt that the T2i is better IQ-wise.