Microsoft has officially confirmed release dates for the Xbox 360 Left 4 Dead Survival Pack (21st April), Halo 3 Mythic Map Pack (9th April) and Gears of War 2 Snowblind Map Pack (31st March), even though we knew at least one of those already. The L4D pack is also due out for PC, presumably around the same time.
The Snowblind Map Pack follows a patch that introduces new Achievements and a new experience system and should be out today according to statements last week. The pack itself consists of four winter-themed maps. Check out the original announcement for more details. It will cost 800 Microsoft Points (GBP 6.80 / EUR 9.60) as predicted.
That's also how much you will pay for the Mythic Map Pack, which consists of three new maps - Assembly, Orbital and the Forge-heavy Sandbox - and which is already available to people who bought Halo Wars as part of Microsoft's attempts to get people to shift genre late last month.
The Left 4 Dead Survival Pack, meanwhile, will be free, and introduces a new game moe called Survival, whilst also enabling Versus mode for the Dead Air and Death Toll campaigns. Survival involves trying to survive for as long as possible against a horde of zombies - a bit like, er, Horde, or other siege games.
We'll have reviews of at least one of the above around the time of release.