I haven't even touched the campaign yet. I'll get to it eventually to unlock the special Ultramarines skin. Multiplayer is just too damn fun. The customization you can get through leveling and challenges is great. I usually run a heavy bolter, quick setup, and iron halo. 3000 rounds a minute to your face. Do you want to look unique? You can. SM has full chapter skinning. All of the chapters are already pre-built. Your armor has multiple pieces you can set a primary and detail color on. There are like 8 different models of armor you unlock.