There is plenty of info on the Theme Park Strategy Board, but here is a snap shot....
Invitations were sent out via email, as this round of testing focuses on the internet side of things, the reservations, and of course the actually facilitating the FP+ program.
It was pretty sweet set up, I picked the day, the members of my party that wanted what rides, and was given reserved seating for Wishes, Main Street Electric Parade and then times to go right up to the FastPass Line for 2 Other Rides, looks like its going to be a cool way to guarantee that you can ride a few must do rides or see a few must see shows/attractions before you even get to the park...