high dude,
Sorry to be the bearer off bad tiding's but as off yet there is no support for spanning, you can use the extend my desktop feature to run 2 monitors (wich will work for supreme commander but not ms flight simulator for ecsample)
Whether it will be supported in future is (I think) down to microsoft as it is to do with the os not nvidea driver's.
Whether ati's eyefinity tech (available on 5870 ect) works with win 7 is unknown, but if it dous and n'videa dousn't follow suit, I will probbably switch to ati.....or back to win xp (as I havn't actually perchased win 7 yet I'm just on the rc)
If you're listening microsoft/nvidea, time to pull your finger out and fix it, or risk loosing million's off potential upgrades...