The Problem with the Matrox Expander is that it shows up to the computer as one, very wide display. The computer doesn't recognize the two or three monitors as separate displays, so if you go into full screen with a VM Ware Windows Virtual Machine, it just spreads it out across both monitors. Its a great idea, but the implementation is a big FAIL IMHO.
Oh yeah, one other very awesome application to look into Deltahoe is VMWare Fusion 3. It lets you run a windows XP, Vista, 7 or even 3.1.1 Windows for Workgroups Virtual Machine on your laptop. Very handy tool!!!