According to the Electronic Arts press release demo of the Medal of Honor: Airborn should "land" at August 23rd. Demo will be available on Xbox's LIVE Marketplace and the PC version demo will be available on official Medal of Honor website.
Demo will let you play one mission called "Operation Husky", a joint allied operation into the island of Sicily. According to the Pre-order on EA's Medal of Honor: Airborn web site, game will be available on September 4th, and according to various sources on the net date is set for September 6th. Trailer shown on MOH: Airborn web site states that the game should be available August 28. We will just need to wait and see.
Just eight days left to wait for the demo. You can check out the trailer on Medal Of Honor: Airborn web site.