One thing that I feel is starting to test the limits of this show now is that there are only so many ways a zombie attack can feasibly play out. It's late in the fourth season now; how many times, in how many different ways can they possibly get attacked and it's still a fascinating watch? Some are still great (the scene with Daryl in the basement room was tense as hell, for example), but generally, the show's approaching its threshold in this respect, for me at least.