Well I'm starting over on medium after about 3 hours on hard. I just don't have a grip on the mechanics and upgrade system yet. A few thoughts:
-not sure if their random level generator is an improvement or not. Hunting for secrets seemed a bit more interesting in the last games. Being bigger as well, I dunno. It's bigger but more empty.
-the menu theme song is brilliant. So good. I wish the rest of the in-game scores were that good.
-super polished controls and gameplay. Even better than before, and that's saying something.
-story and humor not as good so far. Fortune cookie humor is average at best, and most often they're inspirational quotes from famous historical people. Really fucking lame. I can't believe they did this.
-Lo Wang is still funny and his VOs are top notch. Kamiko is decent, not great.
-big departure systems wise from their last games. It really is Diablo in a shooter. Each time you die, you get penalized xp and money. It's a checkpoint system now, no quick saving.
-best movement and melee I've ever experienced in a FP game.