Deus Ex HR is a great game if you know the following beforehand:
- Despite advertisements, play it like a stealth game. Sure you can play it guns blazing, but you get waaay more xp for sneaky nonlethal takedowns than shooting people in the chest with a shotgun. Quick rundown - shooting someone, 10 points. in the head? extra 10 points. max points is 20. points for nonlethal takedown - 10 for man down, 20 for nonlethal, 20 for hand-to-hand takedown. 20 or 50 points, plus other bonus points for staying silent.... I think you get the picture...
- You should not spend the points you get on perks immediately when you get them. Hold on to them until a situation requires a perk you don't have, then buy it. I had to do a lot of backtracking to get to side missions because I spent my point on security hacking 3 when I needed the heavy lifting perk around the next corner to stack boxes and jump over a wall. This happens a lot, especially early on.
- Boss fights suck. The dev team has even apologized for how terrible they are. Just accept it and enjoy the rest of the game.