I just picked this up an have only put in a little time on it, but I'll give you what I've experienced.
While they keep marketing this as an RPG, it plays like a third person shooter. As you level you can apply points to various skills like martial arts, stealth, weapons proficiency, etc. which will give you more talents and special abilities. For example at a certain stealth level you gain the ability to move silently for a short time, another level you can remain invisible for a few seconds, and so on. Lots of weapons and upgrades can be purchased and found on missions, as well as tech like EMP grenades, remote mines, sonic distractors, and more. Excursions are mission based, so no free roaming. And while some missions can be tackled in the order of your choice, it's pretty linear. Dialogue direction is chosen like Dragon Age or Mass Effect but it's timed so you have to respond under pressure. As for how it affects game progression I haven't seen enough to comment.
The two main complaints I have so far is the field of vision seems too narrow, to the point that I came away from the first session with a headache, and sometimes the AI is just pants-on-head stupid. They stay in cover while you flank them and don't move while you whittle down their health, they seem to forget you if you run around a corner...just not up to par with what we're accustomed to. Also, there is this whole "action location" thing where you can take an action from a certain location marked by an arrow, like climbing a wall or jumping down from a ledge. This means that while your character can jump down off a ledge at a certain point, he can't jump down from the same ledge at any other point. Not a big deal but it does seem silly when you can't climb a half height wall here, yet you just jumped a similar wall five minutes ago over there. I guess that's three complaints and I guess I can't count.
I'm kind of torn on it so far. I like some of it but I went into it really
wanting to like it so I may be biased, and honestly I have mildly enjoyed it up to this point, but it seems like it was just poorly executed. As for the RPG thing, I'd maybe class it as slightly less RPG than say Mass Effect 2. I haven't experienced the glitches the reviewers are talking about apart from getting stuck in a wall once, but again I haven't played much yet.
Hope I could help.