I'm hugely critical of the writing and acting in TV shows. Until recently, I probably could have named all the shows I would like to someday own on one hand, because for years, I found television so bad, I barely bothered to watch anything at all.
I have no major problems with the writing or acting on the Walking Dead. The dialogue is a bit kitschy at times, but none of the things that make almost all TV completely unwatchable to me are present, or at least certainly not to a damaging extent (constant oh-so-hip one liners and similar completely predictable/bullshit dialogue devices, mini-plots for each episode which are completely inconsequential to the overall story arch, artificial as fuck cliffhangers inserted at the expense of the quality of the story, the general feeling that they're dragging out threads in the plot to a point far beyond necessary and desperately spreading their material as thin as possible to get as many episodes and seasons in as they can on a limited number of characters and resulting limited number of feasible relationships, tensions, situations, again, completely at the expense of a well-written plot, etc), and I think they're doing a good job of sketching out so many characters in a reasonable amount of depth without making it feel obligatory or like it's weighing the show down. And there have only been a few characters that I felt were significantly poorly acted in this show. The black woman (T-Dog's wife?) in the first season was bad. The sister killed off in 1.4 was average. And I can't think of any others. The acting here is light years beyond most television, IMO.
Maybe I have such abysmally low expectations of TV shows that this show seems better to me than it is, but if that is the case, I don't really care, because at the end of the day, I like it.