I think I'll be selling my copy sooner than later because I've been experiencing the "Packet loss" and "Latency variation" constantly since I started playing the game. I've tried turning off crossplay and the On-demand texture option but it has improved nothing. Multiplayer is unplayable most of the time due to the lag spikes, and hell, I get the errors and the lag even when playing Zombies.
I don't think it's a problem related to my connection as other MP games like Battlefield and Halo run fine most of the time, but if someone knows of anything different worth a try, even at a router level, it would be more than welcome.