Warehouse 13: horrific. It's got to be pretty bad if I can't manage to finish the first episode. Take Adam Sandler's worst movie and turn it into sci-fi. Yech.
Persons Unknown: OK. People who like dark might like it--it feels more horror than sci-fi. I don't really recommend it, but I won't discourage anyone from watching it either.
Day Break: awesome. Just 13 episodes (like Firefly, it was canceled mid-season). Pretty much a cop/mystery show with a sci-fi twist. Very intense (definitely a PG-13), with some great characters and some great actors. It ties up fairly well at the end (in other words, it does in 13 episodes what Lost couldn't do in 121). And yes, Adam Baldwin plays himself, as he does in every TV show he's in. Grade: A-.