To be honest, the only reason I disliked this season was because of how prevalent they're making the imaginary friends. I hated it enough when Harry first showed up, but now we're up to at least three of them, or four if the psychologist really does turn out to be one for Deb.
It's getting as bad as Battlestar Galactica's use of angels, except at least BSG had a bona fide reason for it.
Yeah I can't say I'm a huge fan of those Dexter/Harry scenes either. It was put to fairly good use in the third and fourth seasons I guess, but now their conversations are so banal and predictable that it just kinda feels like episode filler now.