343 Industries, true to their word released a client side update to Halo The Master Chief Collection. The update that was released earlier in the weekend was said to address campaign UI issues as well as some of the matchmaking and party issues. The first pre-season of the online cup for the Halo Championship Series has been announced as delayed till all of the matchmaking issues are resolved.
343 Industries has confirmed that a second client side update is coming next week that will be focused on matchmaking performance. Server side patches have been released that are said to address some server stability issues and should help lay the ground work for the client side patch coming later this week.
While it seems that 343 is on top of the problems, there are still a lot of problems to resolve. From what we understand the developers are working 24/7 to isolate and fix all of the server issues, but the problems at launch have really left a black eye on the entire MMC release.