Opinions on ending of Shutter Island. (spoiler)?

i saw it last night and i cant get it off my mind. it was an excellent movie but i want some opinions on what you guys took from the ending of it..do you think leanardo dicaprio was insane? or that he was normal, and just a victim of one hell of a scandal? i think he was normal because of when he met the real rachel in the cave. this is less of a question and more of me wanting some opinions..thanks