It looks interesting, but I just can't dedicate another whole machine just to a server.  Right now my setup is 1 PC, 1 Laptop, 1 HTPC/Server.
The HTPC/Server handles torrents, skype, backup (I use synctoy nightly to push it onto the server from the PC), Mediaportal for movies/music, and GameEx for emulators.  Right now it's pretty simple - music/pics/docs from my PC is mirrored to the server, movies stay on the server only.  I use VNC to connect to it.
How crippled is the actual underlying OS?  Would I be able to install WHS on the HTPC, and then further install utorrent, skype, mediaportal and gamex underneath it?  
Also, how well does it work with PCs that are asleep? Does it require the PCs to be backed up from to be on all night?  I already leave the HTPC on all night, but I really prefer to put my main PC to sleep when I'm at work or asleep - I just use a batch file that launches the backup prog and then puts it to sleep before I go to sleep.
Also, how much RAM does the client use up on PCs, and how much memory does the server take up on idle vs. Vista/XP?
Basically theres a few features I need it to have before I can consider using it:
1. Can wake a PC up and then put it back to sleep automatically to perform the backup.
2. Can wake a PC up to access it remotely. (I can sleep it myself) 
3. Can set only certain folders to be duplicated. (I really dont need HD movies or downloads duplicated.)
4. Backup will image and restore only the drives I specify on clients. (Really don't need games imaged, just a waste of space)
5. Still has a standard windows install underneath that can run windows programs such as skype, mediaportal and emus, and the "server" stuff stays in the background.
6. Can access its own OS remotely to manage torrents, etc (via VNC if necessary).