Just to add more confusion, here's a review of the 40D in comparison with the 350D and 400D.
Nice things to note for astronomy work:
- live preview (both on the LCD and via the USB2 cable)
- long exposures can be controlled by computer without the need for a parallel/serial cable, just the single USB2 cable.
http://www.astrosurf.com/~buil/eos40d/test.htm
Hanging to get my hands on one to see what it can do.
Turbo