Wow, I really don't think I liked this episode at all and I kind of feel like punching something. More coherent thoughts later.
ETA:
Ugh, I still don't really know how I feel! I think I didn't like it because this episode was just so sad. For Sam and Dean to find out that John kept such a big secret from them, had this other life, had another son. A son who had a mom and lived a perfectly normal life with a dad who occasionally visited and doted on him. It just felt especially unfair for Dean, who's never had a chance at a normal life and all that. As I told Lauren, Sam went to college, Adam went to baseball games, Dean got a shotgun. And then Dean coming to the realization that no matter how much he tried to emulate or imitate John, Sam would always be more like their dad. And it kinda pissed me off when Sam was like "I'll take that as a compliment" when Dean's really admitting that he thinks that the fact that he's not like John means he'll never be good enough, or something. Least that's what it felt like. And THEN it turns out this brother that they've only just discovered is already dead! And they'll never get to know him. Just, sad.
I dunno. I was kinda in a crummy mood before the episode. Maybe I would've liked it more otherwise.
Things I did like: Sam brushing his teeth! Why was that so cute? And aww, clumsy sleepy Dean. And Sam and Dean playing rock paper scissors to see who has to crawl through the vent. Always with the scissors, Dean :P And Dean saving Sam/the day, always a nice sight to see. AND I am soooo psyched for next week's episode! I have been wanting to meet Castiel's vessel for like weeks now, I can't wait. Dean/Vessel is like my secret new favorite pairing. So yay! (Sorry Lauren - I'm sure Castiel won't be gone forever!)