You can't have your cake and eat it, too! Nice viewfinder, poorer handling of noise at higher ISO values. And you don't get to use L lenses (if that matters to you).
The D80 has a .94X magnification factor (based on a 50 mm lens at infinity) and has a slightly larger sensor than the 30D so it should present a bit larger picture. If Wilt's math holds up, this should present about 332 sq mm of viewfinder image vs. the 288 sq mm of the 30D (and about 256 sq mm on the XT). That's certainly larger, though I wouldn't quite consider it as "blowing away" that of the 30D. Definately a plus, though.