A website has release a tonne of info about the matchmaking in Reach, as well as what arena and active roster is. Enjoy : ) 
 
Link: http://www.shacknews.com/onearticle.x/62865

Very cool stuff. I really like that you get a choice of what you want to play before the match begins.

If I'm understanding correctly how the Arena works, then it seems like Bungie has finally found a good way to deter boosting and second accounts. The Active Roster feature is a great addition as well, and I'm glad to hear that they've revamped the veto system to allow players to choose from a list of gametypes. May 3rd can't get here soon enough.

I am less concerned about this than I am actual gameplay. Bungie, more info concerning that please.

Dude, yes. Awesome new additions and the UI itself looks awesome. 

" If I'm understanding correctly how the Arena works, then it seems like Bungie has finally found a good way to deter boosting and second accounts. The Active Roster feature is a great addition as well, and I'm glad to hear that they've revamped the veto system to allow players to choose from a list of gametypes. May 3rd can't get here soon enough. "

Looks slick.

Call it McDonald's, cuz...badabababa I'm lovin' it. So far. I think it looks pretty dang good.

" @crunchUK: Yeah, Active Roster just seems like the natural progression of the Party Details feature from Halo 3. I really like how it is built-in to the main matchmaking menu and updates in real-time; should really streamline the process of joining friends' custom games/MM lobbies. "

This looks very promising. Hopefully Bungie could at least add some form of clan matchmaking? Clan tags?