Just finished the game. Took me 9 hours and 11 minutes on Normal and I was very thorough (found all the feathers and eyes etc.). The opening was spectacular and the ending was too, but everything in between was just average. Battle mechanics were great as always but there wasn't much variety and that made the game boring. Sound/music was fucked up at some points. I ran into a couple of nasty glitches that made progress impossible. I had to reload checkpoint about 6 times during one elevator ride because an enemy fell right through the elevator platform before I could finish it off...thus the door at the top didn't open.
I gotta say it was entertaining though. Graphics were superb, propably the best I've seen on consoles so far. Art was fantastic too. Puzzles and the new abilities were a breath of fresh air, I think they really nailed it. Difficulty was nicely balanced or atleast I didn't notice any significant spikes. Finally the story did make sense so it wasn't a mess after all. Earlier I said that this seems like a true God of War game, but it's just a decent action game in the clothes of GoW.
If you're going just for the single player, I'd suggest renting this one.