I think Red John is Brett Partridge for most of the reasons outlined already, i.e. he matches Rosalinds physical description, his voice, he and Patrick don't like each other, remember Lorelei said she was surprised they're not friends.  

I know Bruno Heller said there aren't any twists but I can't help but think Brett Stiles is involved somehow.  Maybe he's Partridges father?  (Both their first names are Brett, no one else on the show has the same name)  Maybe he's controlling him somehow, though a trance maybe, I know it sounds silly but Patrick is always putting people under a trance though.  And remember how Brett Stiles knew where Kristina Frye was, when no one else did.  And someone knew about Patricks childhood memories, in an early Visualize episode when Stiles told Jane where Frye was he made it sound like he knew everything, at least in comparison to Jane and RJ, which he dismissed as nothing compared to him. And she was in a catatonic state, maybe Brett Stiles made her like that?  But Brett Partridge does the killing?  

In any event I hope Brett Partridge is who the writers/produces/creator of the show go with.

Love to hear more input!