So Reach did indeed launch without matchmaking for the campaign. There have been rumors that Bungie is planning to proved that after launch, based on previously made statements. However, Bungie has yet to set a date.
You can still do Campaign as Co-Op with your friend; you can also set your campaign (and other modes) to
open this allows any friends to join your game at their convenience. Sadly, that is only friend support (unlikely Crackdown 2).
It is worth noting that Firefight did launch with Matchmaking (when it was introduced in Halo:ODST it did not). You want
Classic Firefight as normal is only one set.