The next time you play Gears of War 2 over on Xbox Live, there will be a patch you have to download that adds a new mode for matchmaking.
Social Matches is the new mode for matchmaking that allows players to jump in or out of games without disruptions, including Horde mode matches. This is only available to anyone who has already got all the four map packs, which can be bought at a low price of 800 Microsoft Points, “All Fronts Collection,” for all four.
In addition, the patch includes a host of general fixes, improvements, and balancing changes which are available to all players.