I beat the game on normal and enjoyed it. If you play Horde make sure you get 4 other friends in their with you, it gets pretty hard. I got up to level 10 on insane with some friends and couldn't get any further, but I had to bail and go do some stuff. It was ridiculous. I jumped in on a game and these guys were up to level 41 on normal
. We managed to move up to 43, but the thing that sucks is your power weapons like brute and torque bow don't even seem to do much damage compared to your regular default guns.
Fun game.