Definitely a great game for RPG fans.
You've likely already read about the graphics (not too bad, but not cutting edge), the AI (could have been better), and the "glitches" (they are there... not too bad, but it's not a silky-smooth experience)... yes, you've read about these things, yet are still intrigued to read more player reviews. Good - if you've read all "the bad" and still think this game might be for you, I can assure you it probably is (if it's an RPG that you're after).
Again, this is a role-playing game, and an old-school one at that. The game won't care if you line up a headshot perfectly - it's your stats that will generally the dictate the hit. This doesn't mean you can't clear a room with an assualt rifle if you have no stats in it - you certainly can. But don't expect headshots across the room either.
The reason for the low review scores is likely the disconnect between what is on the screen, and what happens. Modern gamers are used to "I aimed at his head, so I want my headshot". They SEE the headshot lined up, yet here, if you aren't adept in the particular weapon, you likely won't get that headshot. Here's another example: the game won't care if you are "hidden" on the screen - the enemy will hear you if your stealth stats are too low. Conversely, a stealth specialist might be in full site "on the screen", yet they won't notice you because of your high stealth skill. This somewhat harkens back to PnP roleplaying - you made your stealth roll, and you were hidden. That's that.
You have to have a suspension of disbelief to enjoy this game. But if you are able to have that suspension of disbelief - that "I'm hidden because of my high stealth skill, NOT because I'm good with the controller" - then this game is a gem. A pure gem.
It's also a little hard. Games like Mass Effect and the like "try" to be about role playing, but they really aren't. You can "win" in Mass Effect with any character build. Not really so here - you somewhat need to specialize. A jack-of-all-trades is a tough, tough route. Be stealthy, be Rambo, be techie... be even two of the three. But be all three, and have proficiency in all weapons? Probably not a good idea.
If you liked PnP roleplaying, games like Daggerfall and (old) Fallout and Planescape (etc), then you'll like this one. Forgive the few rough spots and "really" become a spy.