How much are you going to use your camera? Are you thinking of shooting more pro or are you going just for more features over a Point and Shoot?

I have the d40 and plan on upgrading to the d80 because it has more features, more lens compatibility. However it is heavier than the d40.

A big reason I went Nikon was because I didn't own any Compact Flash (gigs of SD though), used a d50 and liked the feel of Nikon's (d50 no longer available new), felt stronger and more solid, and some ergonomic features.

The XTi had a better lens capability (Auto Focus for Nikon in lenses only, not body controlled), has sensor cleaning (A big plus if you are switching lenses a lot).

I am by NO MEANS ANYWHERE near pro so I am not buying crazy because I wouldn't need to go that big. They only way I would is if the job paid for it.