Lack of good zombie games.
Sure there is resident evil, that's a decent game, but where are to good defense games like "The Last Stand" aswell as an rpg where you take the role of a survivor. I see there's a zombies live, but I think the creators are idiots, and got the concept backwards. They were so concerned about getting a game out fast that they didn't think that maybe for a second a game where you play as the zombie instead of the survivor is stupid as hell.
Rubicon on IAP:
Almost all iOS spenders don't mind - they're not all tightwads like the tiny but very vocal minority who seem to get off on bitching about nearly free prices permanently.