If you started to get the hang of it, it was pretty fun to me. Of course the best part is being the obscurity, being one of the marines kinda sucked and also that it would get pretty damn dark too, you can have your night vision but it also used one of your perks for that too, which sucked.
Being the obscurity was awesome though, he was invisible but you could see him (like the Predator movies, you can see through him but it's distorted). Also you could run fast as hell, climb walls and had kick ass guns, once on wetwork I climbed to the top of the support beams in the very center of the map. It took some work to get up there, but it as neat to look down and see everyone trying to find you, lol.