ok, i try to stay out of these discussions but since it looks like you really want to know, i will tell you what i think based on using both cameras. the 40D is a killer camera. it feels great, the IQ is great, it is planty fast for most conditions and the 14 bit images are really good. the 3" screen is very nice, the live view is also very nice and overall, the body is just a great upgrade from the 30D.
with that said, after a week i sold my 40D and went back to my mkIIn. why you ask? well, the simple answer is because i think that the 1DmkII is still the better camera. the IQ is fantastic (about the same as the 20D or maybe a tiny bit less), the AF is still the best in the league, the build quality is of course the best money can buy, the speed is more than enough for anything that you can think of and the camera can be tailored any way you like it. now, the 40D does have the advantage of better user interface while the mkII has that weird 2 hand thing going on but you get used to it real quick and than it becomes natural.
at the end of the day, you have to ask yourself what features are really important to you and you should be able to know right away which one you should go with. for me and my bird/wildlife shooting, the build, AF, customization and the ability to AF even with F8 are way more important than 3" lcd (i try to only use the LCD for the histogram), 14 bit images, 10mp and live view. these features might be important to you which is why i said that only you can make the decision.