Alright so, I've played through Saudi Arabia and about half of Taipei, here are my first impressions:
Animation isn't great, but it doesn't bother me as much as I thought it would. Gunplay is pretty much like ME1 where it's frustrating as hell until you get some point in your weapon of choice, and then it becomes much more manageable. The game really, really rewards you for picking what you want to be good at and focusing on it. I've been dumping pretty much all my AP into Stealth and Pistols, with a rank in Martial Arts once in a while. Going non-lethal has been surprisingly easy for me so far, tranq rounds are absurdly expensive but I've been finding enough on-site that I haven't had to buy any more since Saudi Arabia. Silent takedowns are my bread and butter, though, I've probably used them on half of the enemies I've taken out. It's a little goofy that the cameras' vision cone are bright green, but no more than seeing them on the minimap in MGS, I guess.
I really like the characters so far. Scarlet Lake and Steven Heck are my favorites of everyone I've met after the few hours. Heck especially, he's given me several laugh out loud moments in the relatively short time I've interacted with him so far. Even Darcy is a douche, but an enjoyable one. The choices so far have been intriguing. Not so much the dialogue choices (although I do enjoy the dialouge system quite a bit), but more when the game forces you to take a stance on letting a person live or die without giving you a clear 'right' choice. They've definitely made good on the moral ambiguity so far, and I have no idea how the two big choices I made in Saudi Arabia will play out in the endgame.
I do have some gripes about the mission design, though. There are some points (3 or 4 so far for me) where the game forces you into combat with a bunch of dudes and there just isn't a whole lot you can do about it. Since I've been trying to play the game as stealthily as possible and have specced my Thorton appropriately, it's kind of frustrating that they do that so frequently, and I haven't even faced a real boss yet. Secondly, the enemy vision is really inconsistent and weird, it's not always clear when you're safe to move and when you aren't. I've had a guy somehow spot me from behind cover while turning away from me. Also, the lockpick minigame can eat a big bag of dicks because I'm OCD and need to hack every computer and open every safe I find and the lockpick minigame has made me reload checkpoints so many goddamn times.
Despite a certain degree of frustration, I enjoyed it enough to spend most of my day playing it. So that should count for something, I guess.