Finished my first playthrough last night on the hard difficulty, 21 hours, missing 15 or so cheevos, not that it matters. Did a few sidequests, and going back for a second run. Game is really good, but seems like a template (rather a template than a one-off) for more complex, more precise games to follow, whether through a sequel or a spiritual successor.
There are numerous modern games it reminds me of: Bioshock, Half Life 2, Alpha Protocol and Singularity and only on a very few occasions does it feel like its own beast. I haven't played a Deus Ex game since the original all those moons ago so I can't really compare it to that.
My main problem with this game is that the RPG elements are too damn light. By the end you're super human. I had about 8 Praxis points unspent, and didn't feel the need to upgrade at all. I had about 20k in credits and had bought everything I wanted. I had the all-powerful laser rifle and heavy machinegun so could easily just mow through enemies without giving it a second thought. It is possible to upgrade pretty much everything you want to.
Ammo is littered everywhere (energy packs in office desks, really?), and great guns are just left lying there in anticipation of one of the boss battles so firepower really isn't a problem. In fact, because I was a universal solider I had to force myself to sneak around. Stealth is definitely the way to go, it feels much better than balls-out shooting and the takedowns, dragging of bodies etc is really well implemented.
The augs that aren't your standard RPG upgrades feel either under-utilised like the personality checker, which popped onto my HUD maybe four times, or overly-showy like the Icarus landing and its drama-cam. The latter would have been much better left in first person.
Dialogue, story and pacing are all serviceable and par for the course. Nothing outstanding outside of the little details like references to stuff you'd done earlier in the game, or the NPCs' chit-chat when you're roaming a hub world. The over-arching story of global conspiracies, evil corporations and corrupt governments does a good job of emulating its influences from OTT futuristic manga, but comparing it to a movie's story it would fall short of The Matrix: Revolutions. Nonetheless, it's all right, and the music makes it all seem worthwhile.
I think Eidos Montreal have a bright future so long as they focus, delve into the details and don't attempt to make their games too grandiose. The best parts of DX:HR were the small things, not the boss battles, not the guns, and the not the story. There is plenty of room for improvement, and I hope they get on the right track.