If you go into Casshern with an open-mind, you'll be rewarded with a cool film. It's not a revelation by any means, but if you enjoy comic book action, there is a lot like here. I loved the soundtrack too, it's almost constant, building up at the right places and adding depth where the characterization was lacking.
Though, it certainly feels like a film attempting adapt a long running TV series into 2+ hrs- some things happen that don't make a lot of sense and the ending is a typical Japanese philosophical mix. I think a lot of people dislike it because of that, it struggles between anti-war and comic book action. Personally, I really liked it and can't wait to get the DVD, but it's certainly not without flaws either.