This meta wasn't always a monster.
I am the first one to say that I can live without monster-of-the-week episodes. Even in Season 2 I wasn't fond of it. The larger arc, the characters we know, those are the things that draw me into Supernatural. The exceptions for me are the monster-of-the-week episodes in which the show does something different - pushes the envelope, as it were; gives us a perspective we haven't seen; and does something subtly with the larger story. "Bitten" did that for me, and I found it to be incredibly entertaining and unexpectedly powerful. I was utterly drawn in by it, and it's an episode I feel like I wouldn't mind watching again. That's something I can't say for many of the episodes in the past few seasons.
Maybe if you've watched more found-footage/paranormal activity/blair witch style stuff, this would seem less original to you. And it didn't hurt that I found the actress who played Kate to be utterly adorable and completely impossible to take my eyes off. But I absolutely loved watching it. Yeah, there were bits where I was thinking "like hell the camera would catch that" and plot holes here and there, but nothing worse than the usual. Didn't hurt, also, that I felt like this episode was telling a larger story than the story of these three kids. Perhaps too obviously. Perhaps not obviously enough. IDK.
So blame Teen Wolf, because I've been jonesing for another werewolf episode. It's been a while since we've seen 'em. I was happy to get s'more of that. What's also funny, too, is that I think this episode was VERY AWARE of Teen Wolf and was basically giving us a Stiles POV :3 I bet you anything this came up in the writers' room. Undecided whether it was a total ripoff or a knowing homage, and don't really care, so long as it was interesting.
What really struck me about this ep, tho, was Kate's comments at the end: "We weren't always monsters." Granted, that's pretty sledgehammery, but I think that it was almost a slam at the backlash that the guys have said they were expecting to get from the fans at Dean's and Sam's decisions this year. There are corners of the fandom that are mad at Dean for trusting Benny; there are corners that are mad at Sam for not looking for Dean; there's lots of speculation and anger about "how could the characters I've known for so long make these decisions?"
That's the point. Experience, exposure to the darker elements, can drive people to do things they didn't know they were capable of. Being out in the world changes you. Sam and Dean used to be who they used to be, and life has changed them. Maybe for the worse, maybe for the better, who knows. But the fact that they have changed is undeniable, and the question is, are we going to give them a chance? To see who they are now, and to see if they will vindicate themselves and prove that they can still be the people we loved despite the things they've done? I see it as a challenge to the audience. Trust us. Give us a chance.
Challenge accepted. :)