I like the three main actors, and that is about it; otherwise, it is a thoroughly mediocre show, and it has virtually nothing to do with Stephen King's works apart from a few tongue-in-cheek references. You can get that on Family Guy.
I think when the it goes more into the background of the main characters it gets much better. This happens more towards the end of the first season and in the second season. Otherwise what you have is just the 'trouble of the week', which indeed is not too captivating always, especially since they tend to have a rather abrupt conclusion.
I can say this much I was asked to do background again but I couldn't due to my full time job requirements. I was asked to play a "military man" and they even asked me to get a crew cut. The episode takes place in the 1950's and I do believe that season 3 delves deeper into the backgrounds of the three main characters.
I've only seen trailers for the next season of Haven, but it looks like it's going to be a doozy. I really like the show, but it has almost nothing to do with the original story. And while I GET the point of the original story, I STILL found it kind of irritating.
Stuck with it (well actually stopped watching for a month or so and watched some other DVDs), got better. Admittedly it didn't get better until the last 3 or 4 episodes but the improvement was remarkable.
The show has gotten progressively better each season. In the second season the actors/writers came together and created 3 likable leads. In this third season, the show has done a fantastic job of expanding the mythology. On the flip side, the handling of character relations took a down turn as the show fell on old tropes of not having the characters talk to each other or introducing third parties - which scream temporary - to muddle things up.
Too bad, because now that the show is down to the final 2 or 3 episodes of the third season, all the character clutter has been removed and the show has improved because of it.