Yesterday was the release of Killzone 3′s Multiplayer portion as a stand alone, free downloadable title on the Playstation Network complete with all modes (Guerrilla Warfare, Warzone, and Operations) as well as all maps both launch and DLC. However there is a bit more to it.
While the game is free to download it is only free to play until you reach the rank of Sergeant I. If you would like to continue past that you will need to pay $15 and then the full experience is yours. Playing till Sergeant I will be a good way to see if you will enjoy the multiplayer (if you never picked up the full game) and as an extra bonus this coming weekend they will be offering Double XP kicking off Friday 8am Pacific (11am for us Eastern folks). So if you got a PS3 and are looking for something different this weekend give the game and the event a try.