There is something called team server proxy which lets you have long distance teams. It basically syncs with the main team server and keeps a local cache. Its important to have fast access to the team server because slow source check-ins can really affect dev productivity.
I just read this stuff today when reading about tfs2010 (on bharry's blog)
The new 2010 is supposed to be loads cheaper and major improvements so if you haven't already purchased I would hold off for a bit!