The Canon Rebel XTi (not XT) is pretty much the high end of the pro-sumer market, as they call it. It will use all Canon EF mount lenses in addition to its own specialty EF-S lenses. It also has the built-in pop-up flash, which some of the higher-end models don't.
I really like the Nikon D80, I used someone's once and it was pretty cool. I've also used the XT (not i) a bunch of times and it was ok too, but the body felt nicer on the D80.
Unfortunately the D80 is pretty darn expensive compared to the XTi. If price was no object I'd get the D80, but who can really say price is no object when the different is around 30%-40%.
"Space. It seems to go on and on forever. But then you get to the end and a gorilla starts throwing barrels at you." -Fry, Futurama