Here is the full session about Windows Phone 7's marketplace at TechED 2010. In this video you can see the MarketPlace application on real LG Panther phone, a beta version of Trial API and more information about unlocked phones for developers.
An Application must display a new screen 1 second after the user
opens it (can be a splash screen) then the application has a maximum of
19 seconds to make sure that the user can operate the it, if not the
application will be rejected by Microsoft.
You can see the full video here.