Now, I have only played Fog and Ignition, I have only gotten a couple of kills with the weapons, and only played Nightfall for a few hives, but here is how I feel so far.
I love the Maverick in both forms. It is actually fun. Something the Peacekeeper wasn't.
Fog is okay. Kinda the same old jumbled mess of CQC. Probably to make it hard to escape from Michael. He is VERY fun by the way. Great add.
Ignition is great. Nostalgia is flowing. And I greatly enjoy the addition of underground pathways. It's something I wish would've been in Scrapyard.
Nightfall so far is amazing. Fresh, new, exciting, not to mention the Phantoms are a real challenge to kill. Not to mention the Breeder. Oh God is that Breeder difficult to even scratch. Not to mention SCARY. If that thing was real I'd off myself right then and there. Screw pushing forward.
The new multiplayer menu music? Thank you! The old track was annoying.
Gun Game? Eh. No thanks. It wasn't fun when it first came in Black Ops.
Hunted FFA? Shoot yourselves, devs. Learn that WE DON'T LIKE HUNTED. We like our old, missing modes. And Grind is great. Add it.
Cutting Rescue and Point Blank challenges in half? Thank God. I like to play HC only but I force myself to play Core to get Rescues. Lean kills getting cut in half wasn't really necessary. They weren't hard to get. Except on scoped weapons.
Nerfing IEDs? I don't get it really. They were never a problem for me. Sure I died once in a while but that is what they are for. I'd rather everyone have access to OP equipment than useless equipment.
eSports rules added to our Clan playlists? *sigh* Take the challenge away from everything because people whine, why don't you.
So far those are my points. With the exception of a couple things, great job IW! My favorite addition with Onslaught is the Extinction map. I absolutely love Extinction. Blows Zombies away in my opinion. Zombies got stale really fast. By Black Ops I was done with it.