Playing it now, and having the most fun I've had with a new-gen game in ages. Playing at max difficulty, and they really do crank the difficulty for that, making open gunfights complete and utter suicide.
I'm presuming the lower difficulties (the easiest of which is called 'just tell me a story') are a different matter. But the hardest difficulty is called 'I want Deus Ex', and it seems like it is a deliberate 'shout-out' to those who played the original game on realistic. One shot kills you. Seriously. One shot.
So far I've only got 3 augs - one to increase my inventory (necessory, as inventory management is fucking tight - I imagine I'll need a couple more over the course of the game if I'm to carry a decent loadout), and 2 to increase hacking (there are a fuckload more augs, but lots of them are upgrades - need to invest 5 in hacking to hack level 5 security systems etc, plus there's extra augs needed if you want to hack robots and so on.
Augs are merged with the skill system, which sucks, but the massive increase in diversity makes up for it. Weapon mods are in, and are adequately complex (some weapons will only take some augs). Stealth is done really well, especially in terms of noise - there's good reason to get a silencer, and at times a tranq gun might be even better for silencing (though stun guns and tranqs aren't as godlike as in the original - they fixed it by making the enemy act more intelligently during the delay before they go down - even if they don't have friends to take you out, they'll look around for you (and are pretty sensible in whether they can spot you - in the original warehouse mission they spotted me every time, outdoors where I could set up a long-range sniping spot they ran around confused and I could pick them off) and, as I said, one shot and you're dead.
HUGE maps. At least as big as the original, maybe bigger - especially when things open up after the first mission. Lots of sidequests, and lots of hidden sidequests triggered by dialogue with randoms. You can find black market merchants by exploring, to trade with (or rob).
I'm hating the cover system, but it doesn't really hurt you not to use it and it isn't a popamole style system either. It's more there for stealth - you can't sit behind cover and pop out taking shots while the enemy does the same. Instead, you hide behind cover, then press space to roll out into the open (or to the next cover).
I'm guesing that the easier modes are popamole. But with the 'I want Deus Ex' setting, they really do seem to be making a genuine attempt at recreating the feel of playing the original on realistic. Maybe not 100% successful, but compared to all the shit that's around these days, it's just fucking nice to find a game that is even mildly unforgiving.
Oh yeah, I toggled that 'highlight objects' and 'highlight paths' shit off at the very start. Don't complain to me about handholding if you didn't bother turning it off to start with.
Biggest annoyance is the inclusion of boss fights - not all of them are lethal (and some can be beaten through dialogue - there is also an aug that works similar to the empathy perk in Fallout, to help with that) - breaks the Deus Ex feel a bit, because for me a crucial part of the original was that map triggers are never to do with kills, hence allowing emergent gameplay (like turning tail and running from Hermann, yet still triggering the end of the map).
Not saying it's perfect, but fuck - at least pirate it, and buy if you enjoy it. It's the best 'next-gen' game I've played in years. At least so far - you can never quite tell when these games will suddenly turn shit on you and make you look like a fool
Oh - IMPORTANT. One of my main beefs before playing was that they were ruining the theme of the original where the pre-nano-augmented mechs were ugly mechanical husks, scaring kids and scarred for life, whereas Jensen just looks badass. I don't expect this game to follow that for continuities sake, as I'm happy to call it a reboot, but it was just a cool theme to follow up on. I can confirm that despite Jensen's physical appearance, that old continuity IS in. Augmented folk need regular injections of an expensive drug (manufactured by versalife) or else they face constant agony and possibly death through rejection of the implants. Whilst Jensen looks cool, the dialogue indicates otherwise - characters tell him he looks fine (for his confidence), but elsewhere it is clear that people are afraid of him, and that he (like other heavily augmented individuals) is quite horribly scarred. Peoples' reactions range from making lame excuses for staring at you, to outright abuse. I'm guessing that square enix wanted the best of both worlds - they wanted to do the whole 'post-human' thing with the original game's horribly abused augmented agents as an interesting theme to follow up on, but didn't think a game with an ugly protagonist could sell, so they made the graphics one way, and then completely ignored those graphics with the rest of the dialogue/themes.
Edit: kill any civillian is in. First time I've seen that implemented in this sort of game in fucking ages. Haven't tested it with the leads just yet, but I snagged a pretty good assault rifle by knocking out a copper, and since then I've been restocking my assault ammo by taking out cops.
The animated stealth kill/stun is ultra-brief, so it hasn't been annoying me. More importantly, it's limited use. It takes up an energy bar, and you only have 2 energy bars at one time (and only one regenerates without using an item), so it's situational rather than a standard kill technique. Most common method of stealth takedowns is still the stun-gun - ammo is usually more plentiful than energy bars.
2nd edit:
I hate to praise games for 'atmosphere' (because it feels like something you say when gameplay sucks), but these guys have nailed it. I've been ignoring the quests for now and just exploring the current (massive) hub, breaking into random apartment buildings and so on. I've just found Jensen's own apartment (ahead of time - I wasn't even told that he had one yet), and they really do a great job of building the image that this guy is scarred and fucked up - the apartment is littered with painkillers, doing a really good job of showing (a) this guy hasn't been looking after himself since the accident, and (b) he's popping painkillers like crazy since being auged. The best bit though is when you get to his bathroom - the clerk mentions on the way up that they haven't got around to replacing his mirror yet. When you get there, you see why - it's clearly been smashed. Deliberately, and by him.
It's just such a pity that they insisted on making the guy look badass, instead of the freak that the rest of the game treats him as - it's like the writers and graphics teams had two completely different ideas of what they were supposed to do. Punks mock him in the street, when he looks like someone who would be a walking advertisement for how augs help you pull chicks. Still, fuckloads better than expected, and the 'little things' are there.