The trailers make Shutter Island seem like it would be scary. I wanted it to be scary, I needed it to be scary. But it's not scary at all. The movie plays out more like a procedural and whodunit. Stop reading if you're planning on watching this movie. While there won't be any overt spoilers below, the less you know about the movie the better.
There's nothing particularly wrong with Shutter Island except for the fact that you leave feeling unsatisfied. Too many mini-plot holes, not enough successful thriller aspects, and ultimately the movie was ten years too late. If you're going to sit through an unreliable narrator story with an easily telegraphed ending, it better be damn entertaining all the way through. Instead you get some fine acting performances, a choppy directorial effort -- Scorsese is consistently hit-or-miss -- and some nice visuals. The premise of the movie is good but everything just kind of drags. I'm more interested in reading the book (by Dennis Lehane of Mystic River and Gone Baby Gone fame) because it's probably deeper and more psychological.
Actually what is fascinating is reading the Wikipedia entry about lobotomies, and how the transorbital lobotomy was accomplished. Put it this way, the movie got their facts right. They did use an ice pick, they did go through the eye, and there's a mallet involved. Fascinating! The procedure was first done in 1946. We've come so far with lobotomies since then right? Right?