Alright, so I went to a store that broke the street date and managed to beat the game on normal, S - ranking about half the stages. The reviewer's estimates for time spent beating the game (2 hours of gameplay, 6 hours total for one run) are pretty much on the nose. Generally, the flow of any particular stage goes like this:
Intro cutscene -> small section where you fight some dudes / play panzer dragoon -> Boss fight -> End cutscene
The section where you fight guys is always pretty short (my time in chapter 3 was literally 40 seconds or so). These sections do get a little longer as you get farther into the game, but the fighting system itself isn't very deep. You have a basic light attack, a heavy attack that goes into a cooldown, projectiles which are useless on any of the big slow enemies you'd want to use it on, jump, and dodge. Beating up enough dudes lets you enter unlimited mode for a short time which lets you use heavy attacks with no cooldown period. Since heavy attacks can only be used sparingly and bullets are useless, you'll mostly be using jump and light attack or holding light attack for a launcher. Almost all enemies (including bosses) have an attack that brings up a QTE prompt which will let you counter for big damage. If the combat sounds shallow, that's because it is; even more so than the overly reductive crap thrown at Dynasty Warriors.
Unlockables are trailers, cg art, etc. You can also unlock and equip different HUDs that confer bonuses like better defense, but I unlocked a few that do things like make the HUD invisible or severely shrink your life bar that supposedly unlock more things if you beat the game with them. Also, doing well in the main story unlocks a hidden chapter that is basically you playing the last chapter ALL OVER AGAIN to tack on an extra 30 second cliffhanger to the normal ending.
As pure spectacle, and viewed as a collection of interactive cutscenes a la Heavy Rain and Dragon's Lair, it succeeds totally (aside from the hidden ending). If you asked me if I preferred Heavy Rain or Asura's Wrath I would answer Asura's Wrath without hesitation. It does not approach anything like Bayonetta in terms of the complexity of combat but it does get the general mood and desire to be as over the top as possible. I wouldn't criticize anyone for getting and enjoying this game but even if you're looking forward to it I would recommend waiting for a price drop.