James,
I had the original D30 as well and for its time, it was an amazing camera. I'm mostly interested in the IQ coming out of the 40D, especially the RAW files. I'm very happy with the 8.2mpx sensor having worked on images off of a 20D, XT and the 30D. The 5D's are obviously much bigger files but the 30D files are easier for me to process. Guess I'm just used to them.

I'm interested in whether the 40D files are more like the 30D or the 5D in terms of color, noise and cropping room.

As for features, I have had to read the manual for both the 5D and the 30D and I'm still not sure about some of the features (like auto-bracketing). But for what I shoot most -- F8 @ 1/200 manual with strobes -- there's not much of a learning curve

Jim