Hi,
I am getting some good questions on the topic of how the playlists work with First Strike. It is frankly too long to explain well in 140 characters on Twitter.
If you own First Strike you will be joined in a Lobby with others who own First-Strike (or start one). The DLC maps are set at priority slightly above the non First Strike maps. This means they will come up in rotation more frequently. Use your ability to map vote for, or against, any map. If you have First Strike, you will see a secondary tab in your Choose Map screen during Private Matches, Combat Training, System Link and related areas of the game where you can explicitly pick which map to play.
If you don't own First Strike, you will be joined in a Lobby with others who don't own First Strike (or start one). In this regard, it's similar to Modern Warfare 2.
We try not to kick you out of a lobby if you don't have First Strike, but some exceptions are unavoidable. For example, If you join on a Friend who is playing in a non First Strike map, but who owns First Strike, when the game ends and you return to the lobby you will be kicked if the lobby votes for a First Strike map.
If you are playing in a Party with folks who don't have DLC, we will tell you. You can then play as though you don't have it. Alternatively, you remove players from your party who don't have it as you've been able to do in the past.
We have the option of a First Strike only playlist, which you won't be able to join if you don't have First Strike. We have not yet exercised this option, but are considering adding it on Friday at the start of Double XP weekend based on feedback from the community over the next 48 or 72 hours or so. I am preparing as though we will do a First Strike moshpit on Friday when Double XP starts. It's currently getting translated into the many languages the game supports. It's easy to remove (or keep) depending on feedback.
First Strike comes out "around" 2:00am PST on Feb 1.
I say "around" because it takes time to get it out to all the content/cache servers. I can't give you a specific time because it really depends on Microsoft and how fast they cache and populate the download servers. It's not coming any earlier, or later, for any other time zones. Google "time zone conversion" and convert the above to your local time zone.
David 'Vahn' Vonderhaar