This is really fascinating to watch. I've only played the public demo so far. First time I was really turned off -- the camera, the objective marker, the HUD, the QTEs, the darkness, the new mechanics, they all irked me.
Then the second time, I dialed the camera down to 2, the aiming up to 7, changed from crosshairs to laser sight, and dialed the brightness up from the default 20 to 30. I learned to slide into cover, to shoulder-check enemies with a running melee, to do a Vanquish-style slide by running and tapping L1 (and shoot while sliding), to do quick-shots with simultaneous (and subsequent) taps of both triggers, to throw myself to my back and roll around enemies with aiming and X, and to load pills once crafted out of herbs in the inventory. I got a handle on the inventory, which is a huge step up, arranged like PS3's hub menu. I came to see the benefits of a dedicated melee button, one governed by a stamina meter so you can't abuse it, and I learned how the context-sensitive melees are still there. With the slower camera, movement was no longer nauseating. I also no longer found the objective marker or HUD distracting; the latter, in particular, has grown on me, with its segmented health bar making pill management a breeze, and individual shells visualizing exactly how much ammo I have left.
So suffice it to say, it really clicked with the second and third demo playthroughs. That being said, I can absolutely understand where all of the reviews are coming from. The game is definitely a shambling Frankstein's monster of many parts, sometimes patched together inelegantly. But your mileage will vary: I personally love many of the individual parts, and coupled with the dumb bombastic energy powering the whole enterprise, it becomes something more than the sum of its parts. This is probably a bad example, since many people hated the game, but it kind of reminds me of Sonic Adventure 2: I know that objectively the game is flawed on many levels, yet somehow it comes together for a memorable and consistently fun experience. At least, that's what I'm inferring from the demo -- we'll see how the full game holds up Tuesday.