40D defo the one to go for, unless your a technophobe.
I just did the jump to a full size camera, much better balance and feel to it.
However it has more buttons than a pair of longjohns and more bells than the bikes in Amsterdam.
This is one camera I'm actually going to sit down with the manual and study a while.
The 450 will still be the small body, small feel camera. I have absolutely no doubt it will be a corker and offer loads, but in the short time I've had my 40D I have grown to really love it.
Mind you there was nowt wrong with my 350 just had a hole burning in my pocket