For those of you dying to know the shutter count on your 400D, there is an option - it's not easy, but it is an option.
CHDK forum member thaibv has created a hacked version of the 400D firmware that allows you to (among other things, like 3200 ISO) access the "factory" options screen on a 400D. Pushing some buttons will cause a file to be written out to your CF card with the shutter count value in it. Definitely not for the faint of heart nor the technically challenged, but I felt I had to report it, as so many people have asked me.
Detailed instructions at POTN on this thread.