I'm in the minority because i really like this show, it has its flaws, but overall, i think the good outweighs the bad.
what they did very well in series one was the dynamics of survival, the need to join with others vs self preservation, we had double dealing and betrayal, but we also had people failing just because they were scared, which was quite a brave move really.
The second series was flawed but considering it was drastically re worked to fit round Kelly Overton's pregnancy, including the introduction of a complete new major character, i think it worked well considering.
the vampires are the weakest element, and there are truly ridiculous bits like Scab offering the stuffed cougar to head sister, or basically everything involving Scab full stop really. sam's not nearly as interesting as the writers think he is but there is a reason he's there, one of the key themes is about the nature of evil. vampirism is a metaphor for the badness that is within everyone. Sam represents a sort of elemental evil as he has been bad since he was a child, he's had a bad start which has damaged him, but the prison guard offers him a way out, even when he's brutally attacked his tormentors in the young offenders institute, Sam rejects this in favour of murdering people for shits and giggles. an extension of this theme is having characters who return to being human having been vampires, and having to cope with what they've done as vampires.
There's been some criticism of the show having a large extended cast but i actually like this aspect of the show, it helps to make the extended universe the show inhabits more real, i think for a relatively low budget show then do a pretty good job of creating a believable post apocalyptic landscape, particularly compared to the much higher budget shows like The Walking Dead.
from the way this season is going, it looks like they'll be needing at least two more seasons to wrap it up, i'll be disappointed if they don't get them as I'm interested in what will happen and in the continued development of the characters.