I'd been a Nikon film shooter for many years, but gradually my two Nikons found their way into a corner of a closet. About two years ago got bit by the bug again, and after looking and looking, bought a Canon Rebel XT. And now I have two of them, along with several Canon lenses including the image stabilized 200-400 zoom and a Sigma wide angle. I have my eyes on the new Mark III, but that's in the distant future for now. Way too many $$$$'s.
Those folks in our camera club who have the XTi love it.
Consider Nikon and Canon and make your choice bsed on your own intuitons. I thnk the Sony's are also rans. Of course ask 10 people and you'll get 20 opinions.
Remember it's ultimately about the shot you get.
Happy shooting.