If you want to see a movie in which you become emotionally invested in the characters only to have no payoff at the end and feel cheated...
If you want to see a movie that will depress the hell out of you so much at the end that you want to slit your own throat...
...then go see Sweeney Todd.
Would some one please explain to me why people pay to see this play and why it was worth adapting into a movie? Had I actually paid for my own ticket I surely would have wanted a refund.