About realistic mode...
I want to read stories of people's attempts. Treyarch loves to make you run through open areas with gunfire coming from all angles, both onscreen and off, and from what I played of the campaign there is more than enough of that going on here too. Nothing about this looks in any way balanced for a realistic mode. I think they're just counting upon rote memorization and co-op revives to balance out the cheap encounters.
I'm at mission 7 right now, playing solo. My experience so far: this mode was barely tested, much less balanced. Difficulty is all over the place. Some places are brutal, others are very easy thanks to massively OP cybernetics (instant sticky grenade which instantly teleports into any enemy on sight? With infinite ammo? Really?). No enemy respawn or timed sections so far, and the friendly AI actually kills enemies, so you can cheese many of the chaotic firefights.
When you can't use cheesy powers of tactics, the difficulty is high, in all the bad ways. A lot of the 'cutscene-like' moments that are clearly intended as pacing (run through this corridor!) can become brutal. In fact, cutscenes frequently leave you in a place where you are dead in half a second, sometimes not triggering the checkpoint and forcing you to watch the cutscene again and again until you get lucky or perform the right ducking move. It is also mostly based on luck. Sometimes you survive the most stupid shit because everybody missed, many other times a rogue bullet from nowhere hits you even when you are in cover and it is instadeath.
Overall, a very bad experience so far. The last few games were too easy on veteran, but I think this is a step in the wrong direction.