Among the large number of problems with Halo MCC, there is one that so far, its not being fixed, or even mentioned; its the achievements problem. I have a total of six achievements in "Done! Unlocking..." since November. No matter what, they dont unlock.

Now, ODST is finally here. And, the achievements problem is here again. Should I been surprised? No, since Halo 4 have to THIS day a lot os problems regarding achievements, its pretty much clear that all Halo games, or dlc, will have problems of this type.

Here is my advice 343i: if you don't know how to do it; don't do it.
Hopefully the next Xbox OS update can resolve these issues. Apparently Xbox One users can expect some changes come E3.