After buying and using a D300, the D40 feels more like a toy than a real camera.
Yeah, and after driving a BMW for a few years I just couldn't stand my wife's Chevy Malibu either.
Those two cameras are in totally different classes. Of course they feel different.
For the record, I really like my D40, and it's taught me what is important to me in a DSLR so I know what to look for in the next one. I wish it had more AF points, auto exposure bracketing, and an in-body focus motor, but most of the time I'm quite happy with it. It's a great camera to learn on. I see a D90 in my future to address those three issues I have.