Caution: (pre)Review/Bored Wall of Text Below
Managed to get some time in the game tonight myself, and so far I'm enjoying it, though it is a bit rough around the edges. I am only in the first area since I spent a chunk of time reading the backstory to the game and its history. I'm *really* digging the whole artistic feel they have going on and the multi-faction politicking between humans and xenos.
The hacking system is actually one of the better minigame-type systems I've seen. It's a bit akin to an active time battle system in RPGs. You choose a type of action to buff your stats, debuff your opponent, or straightup attack and try to simultaneously counter his attempts. The better your hacking the faster your action completes; likewise for your enemy. Fail, and you can be back hacked with end results from messed up vision with a hacked smiley face overlay on your HUD to outright death.
So far, I've found that for an opponent about equal to my Attack/Defense ratings, I quickly knock down their attack, and if they haven't killed my attack yet I lower their defense before attacking. If they've lowered my attack, I then buff it back up and go all out. Works most of the time. There is some RNG involved, so if you click on the target to hack again, both your stats and the target's stats will change within a small range. Hacking human targets is pretty nifty, and getting them to attack their allies.
The AI is a bit...meh. Nowhere near something like FEAR's, and not really all that great even when compared to run-of-the-mill FPSes. Each mob has a basic AI profile -- snipers stay at distance and try to snipe, shotgunners try to run you down, those with assault rifles tend to do something in the middle. I have seen the snipers try to take cover after I hit them and have been flanked by a shotgun squad while being pinned down by a sniper, but I can't necessarily say that's due to active AI or just coincidence. I do know the enemy usually doesn't respond to an ally dying next to them, though I've been taking down their allies with a silenced sniper rifle while their buddy is walking away.
I can't vouche much for stealth since I'm more of a psi/mobile machine pistol/katana dual wieldling type character at the moment. I do know that enemies have a limited auditory alert zone, but will come running if they see you and have a bit of a psychic preminition as to where you are once alerted. I liken it to an distributed cyber command network ala Ghost in the Shell, but that's just me rationalizing

However, I've had my fair share of stealth kills, even with pistols at close range. Granted, I am using light armor, minimal encumbrance, and not running.
The game uses a L4D-esque AI director and modified respawn system (you can adjust respawn rates), so it spawns enemies/NPCs dynamically based on your current location and conditions. If you happen to be in a firefight in detection range of a respawn, they'll come running. I've had enemies respawn elsewhere after a firefight is over, and they acted normal without being alerted. In the storyline missions, the respawn doesn't seem too bad on default after you clear a level. I have yet to try the sub missions -- just side quests within the main mission area.
I haven't seen the AI respond to dead bodies, but I'm assuming that might actually be a design decision since bodies remain until a softcap or timer is hit before they start to despawn. If respawns constantly spawned on top of dead bodies and reacted, I could see it overwhelming the player. But on the other hand it seems a lot less realistic. Afterall, the respawn system is called "reinforcements"
Prices are pretty high to start out with, but the augments/psi abilities you buy from the merchants I think are not intended to be used at level 1, and are consequently priced as such. They're full-on new abilities, not just an upgrade to an existing system. You have an entire cybernetics tab on your character sheet devoted to upgrading various cyber systems to enhance your stats, though they are also expensive just starting out. If you focused on getting either that one ability you want or that one cyber system upgrade, it's easily doable from the get-go. Research prices vary -- if you extend the time on researching a project it's price goes down linearly. Stuff researches pretty fast anyway, and I've already researched six or seven items by level 8 with just the funds from mucking around the first level, and I didn't even research items for the first hour of the game.
Graphically it's nice, though last gen in terms of some texture resolutions and gee-whiz dynamic GPU effects. Poly counts seem high where it matters, and the level design so far feels like it fits well. Run fast as hell, given that it's using the Source engine. Some reflections seem a bit overdone. There is a full physics system -- bodies float in the water, picked up objects bounce about in a HL2 manner, etc. There's also a nice graphic and auditory effect when you land from a jump or height, showing just how heavy your cybernetic body and armor are. Watch the Major in Ghost in the Shell as she jumps from rooftop to rooftop or lands from a height, and you get the idea.
I actually like the darkness as it caters very well to the artistic style of the game, but on the other hand I can see it being *too* dark at times in terms of gameplay in a lit room. The over-darkness is actually caused by the color system, and the upcoming patch is supposedly going to fix that. In the interim, you can disable color fixing (I think that's it) to brighten things up. Again, personally, I like the deep, dark areas punctuated by clear lighting. It radiates a Bladerunner feel and matches the neo-gothic styling.
Speaking of the level design, so far it's pretty free form. You're plopped in a level to accomplish a mission or objectives. You can do so pretty much however you see fit, even diplomatically. It's kinda hard to get into much detail without spoilers, but it actually is very open. Along the way you can pick up side quests which may be self-contained, or could help you in your main mission. Say you can hack but can't sneak or fight your way past the guards to get within range of the terminal for wireless hacking. Well, there's an NPC there in which you can do a quick side quest, who will then show you an alternative panel that'll accomplish the same thing.
The RPG elements are both good and medicore. Speaking from a character statistics and development perspective, it's very robust. You can customize a variety of attributes that affect your basic character performance realistically, as well as cybernetic enhancements which work in conjunction with your basic attributes. There's even a sanity/mental stress system built in for psionics and hacking where you can be driven mad and hallucinate, though I haven't seen that in action.
When you move over to the story and actual gameplay elements of roleplaying, there are it gets a bit weaker. Dialogue actions are pretty basic fare. It's not nearly up to Baldur's Gate or Mass Effect in terms of dialogue, though you're usually given a choice or two when conversing with your an NPC. I think your choices/actions do matter -- at least at certain times -- since I've read of multiple endings to the game. Major characters do seem to have individual personalities, and the script has them responding to your replies appropriately. They're not exactly deep in terms of characterization and can be stereotypical, but sufficent enough so that your mentor won't be confused for your commander.
All-in-all, I'm enjoying the game a lot. It's certainly rough around the edges -- most notably in terms of translation and writing. The story and dialogue seem to be there, as well as a significant history, but fails to come across as effectively as it could have given a proper writer and translation. A good writer could easily flush out the dialogues, story, and add in notable character development. I have no idea how well the story plays out in the end since I've only played a few hours. An improved AI could really kick the game up, as well as some minor tweaking of the user interface. Also, some better documentation/tutorials would help reduce the learning curve a lot.
Honestly, it's a fun game in my opinion and give a much needed fix as far as free form Deus Ex-style FPS'es come. The art direction is awesome in my book, though is pretty out there. If it came as-is from a big budget studio at a full retail price, I'd probably complain about the issues a *lot* more, though they probably wouldn't be there to begin with. Objectively speaking, without the "indie dev" bias, it really could use some fixing up. Factoring in the price and subjective bias, it's a really solid game. Certainly not for everyone and it's going to be a niche love it or hate it game.
EDIT: Ok, after playing a sub mission, the respawn rate is freaking insane. On regular story missions, the spawn rate is fine. But on the random sub missions...whooo boy. It's like being the last living survivor in Left 4 Dead while having a 50-zombie horde led by a tank charge you. Except the tank is cloaked, has a laser, and all the zombies have automatic shotguns, assault rifles, and submachine guns.