Directors don't come much better than Kurosawa, writers don't come much better than Shakespeare, and movies don't come much better than this excellent combination of the two. Add Mifune's acting, plus a good supporting cast (including a really good performance by Isuzu Yamada), and you have a top-quality, classic film. In retelling the story of "Macbeth" with characters from medieval Japan, Kurosawa does honor to the original and creates a fine achievement in its own right.
Much of the time, when Shakespeare plots are transferred to different settings, what results is only a shadow of the original, because too many directors have only a limited grasp of what Shakespeare's deep masterpieces are all about. That is not at all the case here - Kurosawa shows a great appreciation for the themes and potential of the Macbeth story, and adds plenty of masterful touches of his own, creating a distinctive, memorable atmosphere and characters that come to life in their own right in addition to serving as worthy parallels to the Macbeth characters. There are many fine details that enhance both the medieval Japanese setting and also the important themes of the story itself.
Whether you like Shakespeare, Kurosawa, or both, "Throne of Blood" is an excellent movie that should not disappoint.