I think the bodies u listed here are all good bodies. but i have to agree that the 40D is in a different class from D80 and 450D. the equiv nikon is the D300 to 40D to A700? mabbe not fair to compare like that lor.
Personally I am a nikon DSLR fan (i also own a canon ixus 860IS) and i chose it over canon system cos of feel and handling (my 1st DSLR was also nikon and also my fren is using nikon so we can share lens ).
Rest assured, if u are good, u can take stunning pics with any of the cameras and any of the cam can last u till "amatuerhood" even "semi pro"...
P/S: perhaps it just give customers more confidence when they see a photographer lugging a huge and ex camera?