The first thing of note is the outstanding soundtrack. It's a unique mixture of electro rock and funky synth tunes, merged with traditional instruments and spoken sound effects. If you've seen Miyazaki's highly acclaimed The Wind Rises, you'll remember the amazing train scene with spoken sound effects. Kamui uses a lot of that and it sounds cool. The music also blends in perfectly - when Jiro is with the Native Americans there's even a pan flute in there.
The second thing that woos the viewer is the animation. There are a number of impressive scenes, but arguably the best ones are the ones where characters and objects dissipate into colorful particles that fly around and glitter like in a kaleidoscope. All of this is not that surprising when we look at the production list. Made by Madhouse - one of the oldest studios that constantly puts out high quality content. Directed by Rintaro, also behind jaw dropping visual masterpieces like the Adieu Galaxy Express 999. Key animation by Kawajiri and Takashi Nakamura, whose hands touched a number of extremely cool and stylish animated works.
The third thing is historical accuracy and here we get to the part that seasoned viewers might appreciate a bit more. By no means is Kamui hardcore accurate, but the environments of 19th century Japan and America are pretty believable. The Ainu and Native American tribes are a bit romanticized of course, but it's quite pleasant to observe their habits and attires and compare them to the Japanese.
Another interesting thing to observe is the clash of ideology, culture and religion of the time. The main clash is obviously between the Shogunate and the rising imperial forces that happened during the Boshin war. A more subtle one is between the Japanese and the indigenous Ainu tribes. This being portrayed at all is kind of a big deal, because the Japanese are a bit shy and embarrassed when it comes to depicting their native tribes, because of the complicated ways in which they were "assimilated" (unlike Americans who like to flash around with the heritage of their natives).
The religious clash is kinda connected to the cultural one - Buddhism VS the worship of local deities. It's a common theme, often present in anime and manga too. If you look closely you can draw the following parallels: Tenkai's face = Buddha = the Devil's incarnate. It's not uncommon to see in Japanese literature the tales of Buddhism spreading from Korea or China and violently trying to phase out the local deities. One of the most fascinating depictions of this clash can be found in the Sun chapter of Phoenix, a most influential manga by Osamu Tezuka.
The Dagger of Kamui is a pretty interesting work indeed, although it's not as well defined and polished as let's say Princess Mononoke, on which Miyazaki worked meticulously to atone himself for Nausicaa (which he was forced to do a quick adaptation when the original manga was just starting out). Neither is it as striking as works like Ninja Scroll, but even action fans shouldn't be disappointed as there is enough slashing and slicing to go around.
