lvl 5 is glitchy. There is a zombie that keeps on getting stuck on the screens edge and you can't continue. Other than that, this is a fun addicting game.
Best route to go is to buy the weapons that give you the most rage combined with dodge and heal specials. for the most part, the recharge time doesn't matter. Stick with the handsome blades and the grenades and save up artifacts for the flying dagger abilities.