This one is a bit complicated. I can see why some people hate it but I must admit that I thought that parts of it were pretty great.
The story and plot is a bit so-so with the switching between the awful mental institution and our main character's fantasy perception of the real world that sends her dancing into awesome action scenes with mega samurai, steam-driven undead nazis, dragons and robots. It is young girls dressed in minimal clothes fighting in a computer game universe and it kicks a lot of ass.
It's not that you hadn't more or less predicted the story at the first sign of an upcoming lobotomy but it doesn't matter much, because it feels like watching a series of very cool music videos and I never found it boring like some reviewers have said.
Some of the actors could have been better, the script could have been tightened in places and I would have been happier without the lame voice over at the end of the movie. But at the end of the day it is a movie worth seeing if you enjoy visually stunning movies and young girls in mini-skirts fighting deadly monsters.
It was directed by Zack Snyder and I liked it better than the awful "Watchmen". It is however not in the same league as "300".