Just got Black Ops 2 on Tuesday. So far, it's alright. I've noticed a spike in 870 users. Whenever I play any game mode besides TDM, I always lose. Because I have nooby teammates, or the other team is camping or being cheap. Which forces me to play with parties/friends so we can own. Assault rifles at my level are relatively weak. MTAR isn't that bad though. Since SMG's are this good I will probably be sticking with them. LMG's don't cope with my style of play so I don't use them much. They do seem to be effective in zombies obviously. As for maps, most of them are pretty small. I haven't played all the maps yet but Hijacked is apparently the fan favorite. It is my favorite too.
Campaign has been improved a lot. Create a class was added with of course limitations. Strike Force missions are fun. Different outcomes in the story extends the campaign replay value. For zombies, I didn't play much. I heard that all the zombies maps were small and the fire traps were annoying but I don't have a final judgement on it.
Staying on the mini-topic with weapons my favorites are:
SMG: MP7 and PDW
Snipers: Baillista
LMG: QBB LSW (Or something like that)
AR: MTAR
Shotguns: 870
Like I said earlier, I haven't unlocked everything yet but these are my favorites so far.