Human Revolution is a great game which carries a lot of options.Sadly these options tend to work against the experience.
A.I. - My biggest concern with a stealth or fps is solid AI. An Deus Ex HR let me down on this one. Bad guys loved to roll 'into' my grenades after I threw them. Although I liked the fact that I rarely wasted a grenade, it took out some of the challenge. Additionally was the AI's line of sight. I would be seen through the smallest of gaps from great distances. The gap would be so small, that the character would fall into a back and forth hiccup motion trying to get a good shot, which they wouldn't. The list goes on; enemy sees you but is out of range, instead of crossing the room under cover they just walk back and forth and yell at you. Enemies didn't operate very well on the stairs, in fact some of them couldn't operate at all. If you're seen and you dash behind cover the enemy will just shoot at your cover until he needs to reload. Better yet they announce that they're reloading. Although these complaints see minor, they add up quickly. And a little past half way through the game you find yourself in a pattern, predicting their every move. Of course satisfaction comes with this as well, after all you end up looking like a bad ass.
Augmentations - A really neat system implemented from it's predecessors, the augmentation system lets you truly customize your character. So what's my gripe? Well it stems from the fact that most of the augmentations are pointless. An example of this would be the extra batteries augmentations. If you perform a melee attack, you lose a battery. The protein items to recover that lost battery are far and few between. However if you just use your last battery, it always recharges. Very seldom did I find myself in the need of more than one battery at a time. Granted their are perks like stealth , you go invisible, which eats up your batteries and the extras warranted. But the lack of protein items in game sour this experience. Adding on to the list of useless augmentations would be punching through walls, ( a handful of shortcuts and secret areas which are accessible with hacking or other means) invisibility, ( a nifty trick but it depletes your batteries so fast it's not reliable) move silently, ( I never had a problem with making noise whilst mid-sneak, this augment drains your energy for little gain.) cooldown timer, ( you get a clock to show you when the enemy falls out of the 'alert' state, cute but not worth a precious praxis point.). Subtract those from the augmentations that you just aren't interested in and you'll end up wanting. Although the augments that are good are a must have. They include the Icarus system ( fall from any height without damage, great for exploring and shortcuts) base recharge rate, ( recharge your battery faster) chemical resistance and emp shielding. ( your only concern after those is bullets).
Items - I'm a fan of any survival game that incorporates the bare minimum of items to help you survive. However Deus Ex HR is not a survival game, in fact you work for a company that makes the things you crave. Not to mention you're the head of security! God forbid you ask for a protein bar cause you ain't getting one. The game would be more realistic ( what the Deus Ex franchise strives for) and challenging if you loaded up at headquarters and the various dealers ( few and far between) and then went into combat. Instead you'll find yourself spending hours hunting for little nick knacks or some god damn bullets. Of course if you don't mind scavenging and you play conservatively you will have a decent supply of items. My problem with this is two fold. First off I upgraded my batteries to max first thing, which proved futile. I rarely had a full battery bar in the game, instead just relying on my last, completely rechargeable, battery. Secondly, at various points in the game I was forced to play a way I didn't want to. Being all about stealth and "never being there" I'd find myself in large supply of machine pistol bullets and shotgun shells. The bottom line is that the lack of items is easy to move past and accept, but it's something that shouldn't be there when you have an office to visit, a home to go to, and vendors selling in various places. ( The office doesn't supply you with squat, your house is slim pickings as well, and for some reason all the vendors in town carry a stock of 3 of a couple items at the most. Thanks for the egg head discount and the two boxes of bullets. I'll try not to fire them all in the same place.)
Stability - My last gripe about the game would be the environment, or setting. You rarely stay in one place for too long, and sometimes get cut off from your usual surroundings with back to back missions. This put a bee in my bonnet. The reason is my play style for these games. I like to do one or two story line missions, and then run off for the sub missions. Then repeat. Unfortunately you get shuttled around a lot in this game and are often forced to pack everything in at once. On top of that is vendor locations. The bastards can be tough to track down, with exploring being a heavy part of that. Within four or so missions you get whisked away from good ol Detroit and taken to China. Which is frustrating when all you wanted to do after the last mission was stock up and take a breather doing side missions. Of course there are vendors in China and with the Icarus system it's not that hard to explore. But it gave me a redundant feeling. After all I had just started to memorize the layout of my city and now I'm starting all over again. In my humble opinion, which a game like this the only mission that should take you away from the main city or location, should be the final mission. And by take you away I mean away, you can't bounce back and forth nor can you access either location unless you're at that point in the story. The biggest bane of these types of games is the time spent walking. And you will do more than five hours of that in Deus Ex HR.
So I admittedly went on and on about my complaints ,and didn't even touch the boss battles. But I have to say that the overall experience of the game was great and I found a lot more enjoyable things in it than I did annoying things.