For people that put in the time to know Ghosts, what is there really left to say?
Guns are balanced. Meaning all guns kill you fairly quick with proper aiming skills.
It's more of a gun-on-gun type of game, killstreaks and assault streaks do not really define a game change anymore.
Lag, that is debatable. I have not experienced enough, like in MW3 and the BOs, to really even make me consider rage quitting.
Spawn...well people complained about that. Is it really an issue anymore? Once you play enough and figure out the dynamics of the game it becomes less of a problem. Of course there are still WTH moments, but not as much.
Maps...We have figured out, for the most part, the comfy zones. There are many flanking options to get in an area. Of course, to a seasoned player we take advantage of the people who do not find alternative routes. Easily to be called a camper, but why move from a spot when a person picks the same entry way and feed you kills. If someone figures me out, I move on to my next comfy zone. Map design has a different feel from past CODs, but we learn and we adapt.
Riley - The dog is iffy. I hate him, I love him. But it really comes down to how you play and the other team.
Killstreaks, I do miss the pressence of the AC130 and a Pavelow. But that is my own personal preference. Nobody, in my mind, has been good enough to dominate game after game of getting elite airsupport. There are unused killstreaks though, or the inability of people gaining them to the disregard of IED deaths.
Support Streaks, I think support is the pinnacle of, close late game, game changers. I've seen support (Oracle, Ground Jammer, Odin), turn a 10 point (give or take) losing game, into a close victory.
I am sure there is plenty more to add, and though the dynamics of this game is very different, it is more of a skill based game. People either have the ability to adapt to situations (which is important for this game), or you can sit in the corner waiting and take losses (and be presumably bored).