I spotted on Shacknews this morning that Microsoft has posted the Gears of War 2 Flashback Map Pack up onto the Xbox Live Marketplace for general sale. The collection of five remade Gears 1 maps was originally available via a download code packed into new copies of Gears 2, and the basic assumption was that this would serve as a way to incentivize new purchases of the game and discourage people from buying it used.
The map pack is now available for 400 points, or five dollars' worth of Uncle Sam Bux. There doesn't seem to be any official announcement about the pack's general availability, and the text description of the pack still says that the maps are "available exclusively with an Xbox LIVE redemption code included in new copies of Gears of War 2." So we're not sure if this is an error or not. If you bought a used copy of Gears 2 and want the maps, you might want to get them in a hurry, in case this is some sort of mistake.
Or maybe the split between the haves and the have-nots is causing some of the issues related to matchmaking, and Epic/Microsoft is hoping to unify everyone by allowing them all the ability to get every available map. Either way, if you bought a used copy of Gears 2, there are now five more maps for you to buy.