I was mesmerised by the imagery, and I don't see why it would be regarded any lesser than that of 300. It was interesting to discover that the same director was responsible.
My favorite of the fantasy scenes is the first battle scene, which has three mean-looking Samurai Warriors. The envisioning was near-perfect, and the visual and character design masterful, complete with excellent visual effects and camerawork.
The movie in general is well-made, and has great production design. The music is decent, though too loud, and so are the action scenes. I wish a better action director was involved, since the lack of experience of the leads shows. Perhaps there should have been more time spent training them. The director tries to make up for it with frantic visual tricks (camerawork, editing, and visual effects).
[sidenote] It's interesting that what got me to watch this is Time magazine's Worst movies of 2011, of which this was number 2. It just happens that I was attracted by the plot of alternate realities and a pretty woman wearing a sword. I later on discovered that the movie was generally poorly received, both commercially and critically. Weird.