They did an amazing job with the 4k scan of this movie. If you get the special 4 disc version, on disc 3 they show how they went about restoring it, scanning the original camera negative, then digitally removing all the dust and scratches that had accumulated on the negative. There are lots of before and after comparisons, showing the wizardry that went into cleaning it up and making it look pristine. They showed very good judgement in the restoration, preserving all the natural film-like qualities (grain structure) while removing all the damage.
It's wonderful that such a great film got such a special treatment.