I'm not going to disagree with the responses, other than to suggest looking at the Pentax K-5 (I'm a Pentax shooter) as well. However, plug aside, if you do look at Nikon, I would suggest skipping the D90 and looking to the D7000 instead. The D7000 is an upgrade for the D90 and, with minor exceptions, carries the same sensor as the K-5, a sensor which is demonstrating remarkable dynamic range and high ISO performance, putting them in reach of full frame and medium format cameras, and some times exceeding them. The Canon 60D is also showing great promise in this arena, which I would choose over the t2i as a result.
So... If I was to break down some suggestions:
High ISO - Nikon. It's a touch better than the Pentax option, but it's almost too close to call. However, for low light high speed photography, it's hard to beat Nikon.
Dynamic Range - Pentax. Pentax, for reasons that they only know, aim to the landscape photographer in a major way, something that dynamic range really helps and the K-5 not only sits on top of the heap for dSLR options, it also exceeds medium format as well. It is more expensive, but also carries some pro features the the D7000 and 60D don't. However, the D7000 is close as well, again just a touch difference.
Resolution - Canon. The 60D is a higher resolution sensor and can capture more detail. It's a hair more detail, but in the right conditions that can mean something. Samples I've seen put it close to the Nikon and the Pentax high ISO and dynamic range, helped by the resolution.
So, if you want to capture action in low light, go Nikon. If you want to capture strong detail and color in landscapes and nature, go Pentax. If you want to capture super-fine detail in controlled light subjects, go Canon. However, whichever you pick, you're only marginally giving up on the other two. Very likely, as it does with most of us, the camera will exceed the photographer anyways. :)