It's hard to be familiar with the movies of Takashi Miike. Despite seeing the majority of his films released in America (and even a few that have yet to be released here), it's hard not to feel like I've lost something in translation. I can appreciate the humor, the violence, the plotlines, etc but there are usually parts that confuse me, and his movies typically require repeated watchings. It's not that I'm particularly new to the films he creates or the films of Japanese directors in general ("Tetsuo" creator Tsukamoto is probably my favorite director); the point I'm trying to illustrate is that you have to WANT to appreciate his films. You have to work hard sometimes to get into what he's doing, because he often throws conventional plot points, "hooks" that grab you, and structure out the window. Even his most fairly straightforward films take many detours into the bizarre (see the tank randomly showing up in "Family" or the rocket launcher that comes out on nowhere in at least two of his films!)...
So, it's not surprising that this is one of the lesser-recieved of Miike's works. Using the "hook" of a sword fighting epic initially gets people interested in this film, but seeing no conventional plot or point to what is happening throws people off. This confuses me -- though I definitely didn't grasp everything upon the first viewing of this, I was still instantly amazed at what Miike has set up here: A journey through one man's tortured soul. Even if you don't feel like you understand everything that's happening, you still realize this film is genius -- maybe you just haven't figured out why yet.
Upon repeated viewings, however, I figured out why. As another reviewer mentioned, you have to kind of look in between the lines. This film is powerful, epic, emotional, and even darkly comedic. On the surface, this film is basically just a journey through someone's afterlife. However, beyond that, the film pours on flashy imagery, ultraviolence, and heavy emotion to an almost suffocating degree. In a lot of ways, this film reminds me of "El Topo" -- a movie that is disguised as a genre effort (El Topo being a Western, this being a samurai swordfighting film) that just uses the basic genre outlines and explores topics deeper than have ever been covered in the genre before.
I think those who overlook this film simply were expecting a straightforward swordfighting movie, which this film clearly isn't. It's way better than that, and it's honestly probably the best film to come out in the last decade. Don't write this off after one viewing, it REQUIRES repeated viewings. A masterpiece.