Although I call myself a fan, this is an episode that shows all the weaknesses of Supernatural. And some of the things I love about it.
Let's start with the bad: First of all, the story is shamelessly stolen from an X-Files-Episode ('Detour', Season 5). Check it yourself if you don't believe me. It's something the writers here often do, and it really pisses me off. They take bits and pieces of other movies or TV shows, and present them as if they were something new. They do it in a very lousy way, too. Don't get me wrong, it's not the main plot I'm talking about.
What I don't like as well, is the fact, that wherever they get, it's always a 'pretty' young woman they end up with (well, I'm in the middle of season 1, so maybe that changes). Come on, this is so inkhorn. The characters could need a lot more depth, and it wouldn't hurt if they were looking a bit more like average people. It would give the show a lot more credibility (an yes, even if it's a horror/mystery-show there's such a thing as credibility).
Now to the things I like: I love the earnest moments between Sam and Dean. It's in those conversations when the show really starts to shine. It's when you learn about their characters, when you get to know them and the way each of them thinks. I like the alludes to their past, tiny hints that show you how they have become the men they are.
It's heart rending to see them in those moments, forlorn, when they are nothing more than two boys, searching desperately for their father.
The dialogue is written very well, and the actors put it into practise probably the best way possible. It's enough to make up for all the flaws of the show.