What I really enjoyed about the Spartan Ops mission we played was the way the game mixed up the objectives. Over the course of the level we had several waypoints to follow, switches to hit, as well as a defense objective. Perhaps the highlight of the level for me was picking up one of the Forerunner weapons. The one I found was a bit like a shotgun that simply disintegrated enemies on contact.
The mission ended with a stand off around a mysterious artifact. After the mission players earn experience which count towards their Halo career and can be used to customize their character.