I bought it. It's good. Not as good as 3, but has some really cool new moves in it. The story is kind of meh. I like that the powers are linked to the blades and you can get health, magic, rage, and red orbs based on which power you have on when you kill enemies.
The multiplayer is actually pretty fun too. I haven't put much time into it, but it seems like it goes pretty deep with upgrades if you really get into it.