I've recently had to make the Nikon vs Canon decision on my first DSLR and I plumped for the 550d with 18 to 135 kit lens.
The majority of the cameras in this segment seem pretty damn good. I trawled through loads of reviews etc and the differences were very slight and largely balanced out.
It seems more than anything your making a long term brand choice when buying your first DSLR. Once you've made your choice your going to continue to invest in bits and bobs, especially lenses, that will mean your unlikely ever to change brand.
As well as a general leaning towards Canon that I cant really explain for me it came down to the video capabilities of the 550D, the fact that it has the close to the capabilities of the high end 7D in a smaller lighter body and it will fit in a pelicase 1200.
Sorry guess this doesnt help much