Haven't had much time to play over the weekend but today is the day
As usual the game had/has a horrible launch (server issues) but it seems much more stable now.
The new War mode is fucking amazing. It's basically a sequence of objectives you have to complete/defend (destroy stuff, build stuff, "capture the flag", move a "payload", etc.) in a limited amount of time. It's so much fun. Especially since kills and deaths don't count towards players' K/Ds which encourages playing the objective, and it works. Contrary to other objective based modes people don't just sit in a corner without trying to win the game.
Looks like War will be a core game mode that I will play a lot.
I played one round of Zombies. It seems a little more streamlined for newer players which I welcome. I never really got into Zombies because I always found it a little too cryptic. With this iteration it appears that the "main quests" are easy to understand but still require some exploration. Then there's the obligatory easter egg for the hardcore Zombie players.
Hardcore multiplayer is where it's at, though. Still need to learn the maps' layouts but I'm getting there.
Campaign...need to get back to it
All in all: So far the best CoD I've played since BO3, maybe ever (haven't played every installment, though).