I really felt like they dropped the ball the moment when Dean said he "enjoyed it."

I realize thanks to this discussion that I've been doing my own handwaving on this point; I think I've been reading that Dean 'enjoyed it' in the sense that 'being on the rack was so fucking miserable that doing pretty much anything else was enjoyable,' and that most of his phrasing and characterization of his behavior in hell was due to his overwhelming guilt.