Sucker Punch is nothing if not polarizing. It is basically half a cheesy exploitation flick which was the weaker of the 2 halves, plastered over a very complex, post-modern drama that basically forces the watcher to criticize himself, rather viciously, and then get, "Sucker punched" by a seriously downer ending. If your willing to get jerked around like that, its flipping amazing.
The most important thing to remember is this: When the lights go down, and Babydoll starts her dance, she is, in that world, about to be ogled mindlessly in a tasteless fashion by people who care for little more then base titillation. Then, the section of the movie starts where we in the audience are doing THE SAME THING. The idea is that you re-evaluate your values, and what you view as entertainment. The name of the movie is so accurate, its amazing. Not only the characters, but the Audience to, will get some serious sucker punches.