Having played it I am completely baffled by the bad reviews. Even the production values are [mostly] high and the presentation is slick. And don't get me started on how deep and well-designed the multiplayer is.
This game successfully combined Hack N' Slash and Shooting mechanics. I think the multiplayer is the most innovative aspect of the game because the depth is massive overall. The singleplayer is awesome for any offline experience. Where the singleplayer forgoes stealth found in multiplayer it emphasizes arcade-y hectic combat.