Just got my new cam the canon40D, i used the canon400d for almost an year when i decided to move to this camera. Actually the 40D is an upgrade of the canon30D SLR camera.
I am still discovering the new features on this camera as it is so different to the 400d's features. these are the first things you will notice the minute you hold the 40D
* weight & size (it's a tiny bit bigger than the canon 30D but a lot more bigger than the 400d, don't know if this maybe good or bad to u but it sure feels great in my hands)
* The giant LCD screen
* 6.5 frames per second
* it feels very proffessional (unlike the plastic body on the 400d)
I didn't really notice a huge difference with the image quality (compared to the 400d) but i am sure there must be.
all in all this is a great choice if you are a 400d or the 350D user already and you don't mind the additional coupla hundred bucks. Otherwise i would suggest keep the 400D but invest the money on better optics (lenses)
If you are buying the 40D i would suggest that you buy the body only and select a different lens insted of the 18-55 kit lens.
ps: I am no pro, this is only how i feel and what i think about this camera. i wrote this cause some flickr friends/contacts are asking me about the differences of the 2 camera's.
