According to arne from Naughty Dogs Development team, a patch will be released in the upcoming few days for Uncharted 2 Multiplayer Beta and should contain the following features:
Patch Notes
General
* Grenade explosions now apply damage properly
Matchmaking
* Players should no longer get hung up in matchmaking for long periods of time
* Teams in Competitive Playlist will now be balanced according to player rank
Bug Fixes
* Ranks should no longer reset randomly
* Quitting the game will no longer reset the PS3
* Player collision – players should no longer get hung up on each other when moving through the environment
* Player will now be killed if stuck in falling animation for too long
* In Plunder mode, treasures will no longer disappear during matches