I've heard nothing but great things about the 40D. My friend Bob, of Blackholes and Astrostuff has a 40D. I've always loved how his photos turn out so much more full of color than mine. The major difference is in the sensors on the camera. The Nikon is not an ideal camera for night photography, in my opinion. It introduces too much noise and red color into the photos. The Canons is rated far superior for night photography than the Nikons.
One thing I noticed at the Cypress Hills Star Party (SSSP 2009) in August, is that everyone had a Canon DSLR for night shooting. I had the chance to meet Alan Dyer while there and bought his book (that was co-written by Terrence Dickinson), The Backyard Astronomer's Guide. Even in that book they recommend strongly that Canon is the only way to go for night photography. So, how could I pass up the chance to improve my night shooting of the stars by not getting this camera? Truth is that I couldn't.
I haven't had a chance to use the 40D yet, due to the weather, but hopefully soon. I'll also be ordering the necessary adapters to attach the Canon to a telescope, similar to the set up for my Nikon. As soon as I have some results, I'll post them. For now, I have a picture of the Nikon D80, Canon 40D and Nikon D90, respectively, so you can see how they all look.


