The Samelia flashbacks are not fun. They are not interesting or enjoyable. They are boring, stupid, and take time away from the stuff we actually care about. I may not have liked Lisa and Ruby very much, but Amelia is the first love interest who's actually managed to make me resent not only her, but the Winchester she's in love with.
At this point Sam's not even a heroic character anymore. He doesn't care about right or wrong, he doesn't care whether Benny is innocent or about finding the real killer. He's just one more obstacle for Dean to deal with while HE saves the day.
Sam abandoning Martin the second he gets a text from "Amelia" just shows how far gone he is. He up and leaves Martin, a mentally unstable hunter, on a case alone to fight a vampire they believe is responsible for several deaths, because some girl who Sam doesn't even know is in immediate danger asks him to come help her? He doesn't even think about trying to contact her until he's several hours on the road. What if she needed him for something completely trivial, like helping her move after a breakup with Don? Remember, Amelia has no idea who Sam really is or what he does, so she'd have no reason to go to him (instead of, say, the police) in a real emergency. Sam's actions ultimately lead to Martin getting killed when he goes off the deep end and Benny is forced to kill him in self-defense. I really hope the writers let Dean or Benny call Sam out on this in the future, because if anyone is responsible for Martin's death, it's Sam.
I did enjoy the Dean and Benny parts of the episode. I think Dean was completely justified in sending the fake text. Remember, Sam knocked him out and handcuffed him to a radiator only hours before. Dean managed to get Sam off an innocent man's case, and he did it without actually hurting him. I don't think Dean realized Sam was just going to abandon Martin like that, but Dean tried to take care of him too by telling him the real killer was dealt with and that he needed to find a new line of work. Again, no violence, at least not until Martin kidnapped Benny's granddaughter and got himself killed.
This episode would have been a solid 10 if Sam and Amelia were not in it. I admit I've always liked Dean more than Sam, but this is the first season I have believed Sam to be an active detriment to the show. The writers need to scrap Amelia and start trying to build Sam into a likeable character again, because at this point if we ever come to a Sam vs. Benny confrontation, I'm going to be rooting for Benny.