I have no particular preference for knowing/not-knowing the unsub at the beginning nearly so much as having all the narrative ducks in a row. I can enjoy a story equally well with a "Uncanny Valley" reveal or an "Omnivore" surprise as long as all of the contingent parts make sense and fit together. But as soon as you throw in an "Epilogue"-like fuckery (like Dr. Spencer Reid not knowing that stimuli experienced during unconciousness is completely quantifiable, no mystery there) or lolwhut like the supernatural "ambiguity" in "Demonology," or Reid saying that 2 seconds of exposure to a pathogen = 20 minutes... I am jerked right out of the story... and am rather pissed off.

My favorites, and I wish we had more of them, are the non-psychosexual whodunits. Like "Derailed," "Won't Get Fooled Again," "The Tribe," "Hopeless" ("It was fun, boss" OMGPERFECT), or "Penelope."

DragonLady