Darkness. No Parents.
Played this for about an hour last night and yes, its very engaging and slick. The combat does indeed feel smoother, the keyboard controls are instantly familiar from previous titles and the graphical fidelity is indeed of a very high standard. The opening scene is original (press Space to do what now??), amazing and horrifying all in one go and sets the tone for a darker Gotham than you might expect.
That said, even though I run on a fairly powerful gaming rig (AMD 8 core, watercooled, GTX Titan) that can churn out GTAV in full detail, I had some very noticeable stutter when driving the batmobile (oh god, yes!) which appeared to be related to the motion blur/depth of field setup; the usual criminals. So, off to the menu I went only to find that I had no option to decrease or remove those effects! I'll take a look at the config files tonight, but that's something of a shortfall in PC configuration settings and will make the game unplayable for a lot of players I suspect.