I played BO1 for two years, and I've been playing this game for several days now. The game is a complete disappointment.
My chief complaint is that there is no lobby leaderboard. I believe Treyarch intended for better players to stop bouncing when they see weak players, to make the game more approachable. The problem is that the when weak players inevitably quit, the rounds stop being ranked. So there really isn't an incentive for better players to play with weaker players in a four player game, other than to stat pad revives. The end result is that the game is less approachable and more fractured.
Even more problematic, since 4 players is unplayable, is that you can't get a ranked 2 player match without coordinating with friends or randoms to dropout of the game lobby at the right time. I spent nearly an hour doing this with my friend to get the one and only 2 player ranked match I've played.
The other problem I have is that there is no meta-game in BO2. Like BO1, you can't kill zombies efficiently after round 40, yet there isn't a fire pit like in Kino, or traps like in Der Riese. BO2's Nacht Der Untoten equivalent - Bus Depot - doesn't have a thunder gun for rounding up and killing in bulk quickly and efficiently. Box-hittin for the ray gun on 40 is simply too boring. The ability to advance deep into the rounds has been taken away. Why reduce the depth of the game???
Another final point is that the circles on this game are far too easy to run, and the zombies won't even hit you in situations where you'd take a down in BO1.
I passed 70 and 80 on most BO1 maps (and 40 on Bus Depot - Survival), so I'm not some whiney idiot who has no basis to put out an opinion. I know how to play and I believe this game needs BO1 matchmaking. The current set up is maddening and makes the game flat out unenjoyable.
On the bright side, Nuketown zombies is brilliant. If only I could get a two-player game in that.