Here's a Vista feature I didn't know about. RDC in Windows Vista supports spanning multiple monitors.
Ivan Brugiolo from the Terminal Services Blog has the details
One of the new features of the Terminal Server/Remote Desktop Client in Windows Vista is the support for multiple monitors. If the machine running the TS-Client has a multi-monitor configuration that creates one logical rectangle, then the TS-Client can span over all the monitors, creating one virtual desktop of the combined size.
Once my M4 gets back from the shop I might have to try that out...