I'm probably not going to play this game all that much longer into the future -- although I imagine I'll still get drawn in once a week with the same friends I've been playing it with since Halo 2, even if the custom options aren't as rich. It's philosophically too different to what I loved about Halo, and philosophically too similar to other games that offer a deeper 'metagame' and so on if that's what you care for.
I'm having a lot of fun running and shooting, in a way I didn't nearly as much with Reach, but there is too much emphasis on the individual's experience, on XP, on personal reward rather than team accomplishment, on onanistic gratification across a 'career' rather than shared victory in games that matter -- on Binary Rifles dropping from the sky and advantages accruing from the Start menu rather than cooperation and planning and parity and contesting the map.
Sometimes I feel I'm alone on these maps fighting endlessly respawning, endlessly rushing bots, and that my friends are meanwhile on another map somewhere, fighting their own bots, and we all die frequently because of things we have little control over, and we all kill frequently because of things our opponents could never have anticipated. And we never achieve anything together, except in a very abstract sense.
Halo 4 is lonely to me. That's probably it's worst sin.