According to AceyBongos, there is a new Assualt Heros Trailer on Marketplace for free download. Here are the details from Acey:

Assault Heroes Trailer: If you haven't experienced the joys of Assault Heroes' top-down shooting, download this trailer for a taster and then get the Xbox Live Arcade game that everyone loves. The trailer is free and available everywhere, and you can download the game for 800 MS Points now.