I'm still watching religiously, too, but I'm really engaged by the whole thing. I was kind of upset when Sheriff Carter turned out to be a bad guy, but I'm amazed at how well he plays that role-- talk about a character you love to hate.
The mysteries they've set up are very intriguing, and they keep giving us more information without answering anything. That's fine as long as they don't pull a Lost
on us. It seems that William and Audrey are mad scientists or sorcerers from another dimension who decided to torment Haven for their own amusement-- due to the time differential, this has been going on for centuries. Agent Howard seems to represent another faction, maybe that world's law enforcement. Who knows? But I can't wait to find out.
As far as the other characters' seeming lack of curiosity, that's a fair point. But, on the other hand, these people are already steeped in weirdness, and their main priority is dealing with an escalating crisis.
The ratings, as far as I know, are stable compared to last year. Given that and Sciffy's history, I'm fairly confident that we'll get one more year. They may be setting up this year's finale to work as a series finale just in case, but I'm cautiously optimistic.