As a single-player experience, I feel the MCC is good enough, but I realize a lot of people still feel burned by the shortcomings in MP. From everything I've ever read, that project was a nightmare that sounded a lot easier to pull-off on paper than it was in real-life. It took longer and cost more than they ever anticipated and even then it still has some major issues. I don't expect them to ever fix it the way people want it to work due to the costs involved that they would never re-coup.
That being said, it's not that the 360 Halo games shouldn't be BC, but they probably shouldn't have made an announcement about it. If they were smart they should've just quietly showed up one day. By making noise, they're just re-opening old wounds and creating an opportunity for MCC bitterness to surface again.
They're not charging us to play the older games we already own on the X1. Both Sony and Nintendo do this so that's worth something.