^it'll be more durable but thats about it really, at least compared to the 450D. the 450D is a pretty significant upgrade to the 400D, with things like live view, faster frame rate, increased ISO range, better battery, a redesigned grip, a 14 bit analogue-digital converter from the more expensive models and a new range of IS lenses to go with it. it will also take SD cards instead of CF, but cards are so cheap now that that isn't really an issue. basically its a pretty legit camera targeted more at where the Nikon D80 was - the 450D will be better than the D80 if terms of features at the moment (Nikons working on a new model to be released near the end of the year I think). The 450D isn't replacing the 400D its a new model, kinda like one up from the entry level 400D. The only weakness of it is that it has a plastic body and it doesn't have a PC socket if you're gonna be using complex flash setups, but im pretty sure you can get hot shoe adaptors for that purpose.