Okay, here's my impressions so far.
The story has been a bit slow imo, but I guess it is a good thing, having a build up for the game. though since I'm at level 3 of the campaign already and it has like 8 levels, I'm a bit worried.
The MM is awesome! Feels very competitive, and is most of all fun! Thank god there is a ranking system! Haven't tried Spartan Ops yet, but will soon enough!