Hi,
I think that having SideShow Gadget support for WHS could be very usefull in many way for the "home user".
1) used with case Screen, it could help having info from the server (t°, HDD space ...)
2) in some case, to have accurate info on the sideshow device, you MUST wake the computer up. Since WHS is always up and running, having him fetch some data (RSS feed, pictures from the net ... could push even more Sideshow as a standard).
3) I would just love WHS to do foo 
thx
Atomusk