"Aguirre" is a stunning, beautiful piece of music. The marriage of that piece of music with the incredible opening shot of the expedition heading down the side of Macchu Picchu is one of the most breathtaking moments in film history for my money. This record stands on its own as a masterpiece, though, and only two of the pieces were actually used in Herzog's film.
I just saw the film. It is amazing, the soundtrack does it justice! Possibly the best film ever. What would it be like if all films had soundtracks by Krautrock (or Kosmische) bands? Conrad Schnitzler really should have done one.