Never played this series before but love the genre. I played the demo for 20 min and here are my impressions:
1) Sidekick is hot
2) Can't move while aiming? TERRIBLE.
3) Viewpoint is horrible; it's neither first person nor third, so unlike a first person you cannot get a good vantage point and unlike, say, Grand Theft Auto, you don't know exactly when somebody is behind you, either until they are right there. It's just not right.
4) Aiming = terrible. Aiming = awful. Here's why: Even on the fastest targeting mode the guy turns SUPER FVCKING SLOWLY. Moreover, and the worst, there is no targetting reticle (that I found; I didn't look in depth in options, though)--just a silly laser sight. The result of this is that as you sweep the sight over an area, you don't really know how close you are to a creature's, say, head until you are literally on it. The fact that you are constantly viewing the laser line from the side (as this is a "side" third person view) means that it's exceedingly difficult to really tell what you're about to aim at until you are, if it changes distances (as a person would if you're sweeping an area and the target is much closer).
In the end, I found that fighting in that congested room near the beginning to be quite frustrating. I never felt totally in control of the guy. It felt like a bad dream you know the ones where you cannot fire a gun no matter how hard you pull the trigger or you're trying to run but cannot gain traction and it feels like running on ice or something.
I'd say that if they made the targeting movement MUCH quicker and gave a proper targeting reticle, plus probably made the view either first person or much longer distance third, it would be better.
EDIT: You know it's funny everybody has the same complaint. There is no way in hell that the testers didn't give the design team the same feedback while playing. I can only assume that one designer with trump power really has a hard-on for this poor gameplay style or that they want the game to fail. I certainl would not pay for it with its current control scheme.