The episode "Olivia" is like nothing I've seen (except the prisoner remake, now that I think about it). It has a scene that reminds me of an experience I had while under the influence of welsh rarebit. I figured out how I could go insane. If my memory was screwed up from brain trauma, or if someone gave me a drug that changed my memory, I would have no frame of reference.
I like the series, in general.