I was amazed.
The episode was amazing. It chronicled Castiel adjusting to his new, human life extremely well, focusing on lots of points that many other shows would simply have skipped over. It highlighted how he was struggling to deal with ordinary things like urinating, hunger and emotions whilst still having an interesting enough plot to keep the viewer engaged. I was captivated. Misha's acting was brilliant, and you started to see hints of 2014!Castiel, which gave a lot of things to think about. (There's another thing - there has been so much speculation that things are heading towards the season 5 episode The End. Castiel is a drug and sex addict in that episode - so how can him having intercourse with someone be unexpected?).
I was equally impressed with the transitions between Ezekiel and Sam - both Jared's acting and the special effects made that very clear, and Dean's reaction to the regular changes was perfect. Perhaps not much has been suggested about the main plot of the season yet, but this episode still advanced the series quite significantly and prepared for something big to happen in the coming episodes.