FYI, for ati users, setting your multiple monitors for infinity mode works. However my framerate dropped to next to nothing. I didn't attempt to tweak it (I had everything at max) and it's possible that my drivers were at fault (either the eyefinity or crossfire portion). I just set it back to normal.
Here's a screenshot of 3-monitor.
http://i59.photobucket.com/albums/g311/brafish/Civ/Civ5Screen0000.jpg
Here's a screenshot of 3-monitor.
http://i59.photobucket.com/albums/g311/brafish/Civ/Civ5Screen0000.jpg