I've seen variations of this movie before (without looking I can bet my life that 99% of reviews will mention Shutter Island at some point, so mostly this was a 150-minute exercise in frustration. Basically I just wanted to figure out what the big twist is so I could go home. Instead I get two hours of characters being stupid and mysterious for no reason and generally pissing me off. No matter how this movie ended I would've felt cheated.
I like the look of the film and the turn-of-the-century feel to the sanitarium. I also really enjoyed the performances for the most part.