Just finished the campaign. It was probably the most fun campaign since the original Halo, but it was also the least interesting (ODST excluded of course). The story felt more like ODST 2 than anything, and I really didn't care about most of the characters. But still, for the most part, the missions were a ton of fun to play. Although some of it really dragged toward the end with certain battles lasting way too long.
The multiplayer is godlike though.