The first season has been a success. It's definitely a classy piece. I have my doubts about the actual implementation of the concept. It is interesting to notice that the series creator, Frank Darabont, has decided to fire all the writers. The plan is to borrow the Torchwood model - use freelancers hired new per episode. Some people say this is because Darabont does not 'play well with others' and ended up rewriting every episode to his own needs anyway. Others think it is because the script quality wasn't as good as it should have been. It remains to be seen if Darabont is aspiring to something he has not yet achieved, or if he just wants a compliant bunch of script robots so he can carry on as he is.
I am glad to see a series that is trying to develop a sophisticated SF storyline, trying to develop the human meaning of a genre cliche: in this case surviving the zombie apocalypse. I don't think it's as good as the non-genre headline drama AMC has put out - too busy, not enough down-time, characters too hastily put together. I get the impression that most of the interractions between characters are plot-steps, rather than windows onto their minds. In a genre environment like that I think you need to develop strong, simple, charismatic characters (as in the best Star Trek or X files for example) and I don't think Walking Dead has achieved either complexity or compelling simplicity of character. However, cripes, it's streets ahead of most genre stuff. Could go either way.