My first impressions, as someone who still plays a good bit of COD, is holy smokes is the sound design better in this game. I'm playing with headphones on and everything sounds impactful, from the explosions to the gunfire. There's also a fair of bit of chatter from other characters that alert you to where the enemy team is. At times it can be a little OP, kind of like having an auditory UAV up.
The time to kill is definitely longer than it has been in past games, I feel like gun fights have a little bit more play to them now. I like what they have done with divisions, and how you gain passive perks in each division as you rank up.
As far as gun balance, it's going to be hard to find a way to balance the fully-auto smg's with the semi-auto assault rifles. The M1grand hit's hard, but given the high TTK in this game, if you are in a 2-v-1 situation it's going to be tough to win that gunfight.
Overall I like the feel of the game, the hit detection seems on point, the sound is much improved and the guns all feel like they have a purpose. If you get a chance to play I highly recommend you try the incendiary rounds you get in the expeditionary class. This is still very much COD, but it feels like a good one. Now I'm off to mess around with War mode.