It's October 2015:
MCC Matchmaking seems completely broken. The last few days I have had nothing but "Searching for Players..." then "Players Found" then "Restarting Search" for hours.
This may be the most frustrating matchmaking experience I've ever had. Just five days ago I had no problems whatsoever getting games in any playlist--Team Doubles, BTB, Action Sack, Rumble Pit, etc.
Now I can't even get a slayer game to load at all. I love this game because of matchmaking--the campaigns are great, yeah, but Halo has consistently the best skill-based pvp dynamics, and I'm terribly disappointed that 343 can't get it together whatsoever to make online pvp consistent for MCC.
After reading everything in this thread/having played Halo since H2, I know this is a recurring problem. That perhaps makes it most frustrating. Just put the effort into making Matchmaking work.