http://www.gameinformer.com/b/features/archive/2012/09/28/the-playstation-all-stars-battle-royale-roster.aspx
The Beta is up as of today for PS+ members. There are two stages and you can play as Kratos, Sly Cooper, Parrapa The Rappa, Sweet Tooth, Fat Princess, and Radec.
Personaly I find the roster to be pretty disappointing. I understand getting that rights to use all of the characters may not be as easy as Nintendo but the list is still baffeling. The levels are about the same size as the smaller levels from the Smash Bros. series but with plenty of dangers added to them to ramp up the chaos. The gameplay is fun but I honestly can't see it beating Super Smash Bros. quality wise.
Kratos was by far my favorite character and thats mostly becuse he seems far better than the other options. His attacks are fast strong and wide ranged.