I like (Win)HTTrack and i have used it a LOT the past few 
months (more and more of my courses no longer have a 
printed manual but provide a website) but i'm just missing 
one little feature: an option to shut down the computer and 
power off when finished (similar to Nero). That way i could 
start the mirroring an go to bed/out/whatever.

This might seem quite trivial compared to all the other 
improvements you are planning to make to HTTrack, but i 
think there are a lot of people out there who could benefit 
form it and it should be really simple to implement:

it could be as simple as adding another checkbox (next to 
the one to close the connection when finished, you're using 
MFC right? so that should be a piece of cake) and calling

ExitWindowsEx(EWX_SHUTDOWN | EWX_POWEROFF) (perhaps with 
EWX_FORCE flag, too)

I 'd have a look at the sources myself, but a college 
student like me doesn't have much $$$ so i use MingW32 
instead of M$ Visual C++.