It took me some time this evening, and some helping/shaming by Dan Hinojosa, but I got X running on 2 monitors nicely on the MSI Wind. So I'm posting the xorg.conf details so I can find it next time I need it. :)
First, to conserve memory, X caps itself at the maximum resolution of the monitors it sees when it's starting. You fix that by adding the "Virtual" section to your Display block.
And in the "Device" block I added a few performance tweaks I found on the web.
It's still not as snappy as I'd like (and as I'm sure it can be). Anyone spot anything else I can add?