Some people have been able to d/l the Lost Planet demo as it has shown un as an E3 advert. Apparently it hasn't appeared in the marketplace properly yet though.
It's true. Seems MS accidently upped it to marketplace lol. A mate of mine on XBL saw it there for a few mins before seeing it vanish. http://koti.mbnet.fi/tiong/x360/lostplanet/
wonder when they are releasing that then Im guessing they gonna do like a demo a day or something because look at the strain from this TDU demo