Surely you know what the difference in specs are. The 40D can shoot faster, focuses more accurately, has somewhat better resolution, and a substantial improvement in color/tone rendering if you shoot in raw. I think those are, except for Live View, the main improvements.
Can you use those features? Do you use raw? Do you post process your photos? Do you print photos which are larger than 4x6? Those are some of the reasons to move to the 40D.
I have had my Canon 30D for about a year and like it a lot.
An opportunity has come up where I can sell my camera at which time I would buy a Canon 40D
What I would sell it for and the price of a new 40D would be right at $400.00.
I know there are a few people on this forum who have the 40D and my question is, is it worth $400.00 to upgrade.
I have played around a little with my son-in-laws 40D but not enough to really know what the pluses are other than live view.
I like the 3" LCD over the 2 1/2" but I don't know much else about the 40D.
I would appreciate any advise.