Supernatural is improving. I still don't have a crush on either of the boys, which feels wrong. And after consuming this kind of fiction all my life, there are certain elements that come across as stale. On the other hand, there are others that my brain automatically begins to dissect so I can decide how I want to approach them in my own stuff. You know what a tulpa is? It's an android in an urban fantasy setting, that's what. And demons are the fantasy version of alien races.
I don't think I'll ever use demons, though, because I've never seen anyone make the concept of them that interesting. Supernatural's bringing in angels too, and I'm not sure if that makes it better (because it's less common) or worse (because theology doesn't translate smoothly to folklore). But Castiel himself is clearly a good character and already breathing new life into the show the moment he appears.
The other thing worth a change of heart is that there have been a couple of excellent one-shot episodes, like the Groundhog Day style looper. I think I've mentioned before that I prefer to get my humor from other genres rather than watching comedies, so I very much appreciate when SPN makes me laugh.
Right now my plan is to finish the five-season arc and see how I feel. Anyone's welcome to change my mind. Or just share your own opinions on Supernatural, sans spoilers through S3.