In their weekly update, Bungie had plenty to say about the new matchmaking in Halo Reach.
Let’s say you want to play some Team Objective with three of your friends. Neat-o! You can do that. From the title screen, select Main Menu, then Matchmaking, and use your Active Roster to form or join your squad (more on that later).
Once you’ve tinkered with all the options, select a Playlist and then choose Team Objective from the list of awesome options. Matchmaking will then begin its search for a suitable party to pair you with. Since you’re operating in a 4v4 list, you don’t need to worry about being split and since you’re in a preformed party, matchmaking is gonna do its very best to pair you up with another party of four in the interest of fair play.
That bit you read over at Shacknews about parties being ravenously torn apart would only pertain here if you had a party larger than this particular Playlist’s team size allows. (Because you can’t have like six dudes on a four man team, dig?) You don’t worry to sweat the calculations though – complex algorithms ensure that these maths don’t ever get fuzzy.
If you’re going it alone, or going in with a party smaller than the max team size, matchmaking will initially try to find players and parties of similar constitution to pair you with. Oh, and through ALL of these scenarios, we’re using an updated version of Trueskill to ensure fair and competitive matches even though it’s not being displayed or being used to inform your “rank” anymore. Trust us, it’s there.
There is PLENTY more, to read the full Update, and to view all the latest Bungie Updates, check out Bungie.net.