Singer does give away some spoilers for season nine here. It's what producers do. I do love what character he compared Crowley to! Although, I'm thrilled I also got to ask him a burning question that's been posed many times by fans on this site, what happens when good continuity goes bad. I have to admit, he gives an answer that I can relate to when putting myself in his position.
So, SPOILER ALERT!, and enjoy the wisdom of "Supernatural's" most senior member of the team.