Without knowing much of the history, I found this to be very absorbing - slow tempo or not - and Teshigahara's understated style is perfect. The performances (especially the title character) are top-notch, and the heavily detailed sets are stunning.
That noted, the DVD available in the US is one of the worst I've ever seen - the pan-and-scan, along with butchering Teshigahara's marvelous compositions, also renders the subtitles unintelligible in spots, and they disappear in brightly lit scenes. The DVD picture quality is grainy, washed-out and blurry, and several weird cuts (especially the scene in which Stefano leaves) betray a transfer from a hastily (or sloppily) edited source. The film is great enough that I'd encourage a viewing, but beware that (if you watch the DVD) that the quality will be atrocious.