So I decided to set my work VPN up as a demand-dial connection on my newly-virtualized PDC at home.  I ran into some bugs getting it set up to work for my whole network, so here’s what I did.

1. Set up the routing and remote access role on the PDC.  This can be done from the “Manage your Server” thing. This part’s pretty easy — just check all the options when you set it up.
2. Create a new interface from the  Routing and Remote Access MMC Snap-in.  Set it up as a demand-dial interface and configure it via the wizard.
3. Ping an IP on your remote network from the PDC to make sure it can dial on demand.
4. On the routing->general part of the snap-in, add a new routing protocol, and choose NAT.
5. Move down to the routing->NAT part and add an interface.  Add the VPN interface from step 2 and set it up as the public internet facing interface.  This will make it masquerade the traffic.
6. Ping your VPN network from a machine on your network other than the PDC.

Should work fine.