I recently acquired Supernatural based on a few positive mentions here on KIA2. I quite like it, but it's a bit... off. These sorts of shows are really about the banter and camaraderie, with the monster stuff being almost incidental. Somehow the chemistry/banter is not quite working for me.
Should I persevere?
It does get better along season 2 or so as the actors became more comfortable but the rest of the show definitely goes completely bonkers and off the rails.
If you do persevere, I highly recommend stopping after season 5. It tells a complete story, was the original 5 season plan of the director and after that he left and everyone they filled in drove the plot into ground and made the show go way way to long on.