This new remaster looks phenomenal to me. I'm used to the most recent Blu Ray disc, and even watching on an SDR 4K screen, the improvement in picture quality is dramatic.
The most noticeable shot to me is in the egg cave under the Space Jockey's room, when the blue laser light shines directly into the camera. On the Blu Ray, it's really oversaturated and totally blown out. On 4K, it's controlled and smoothly graded. Speaking of that, a couple of wide shots in the Space Jockey's room are way oversaturated on the Blu Ray but nicely modulated on 4K.
Not to mention the subtle but significant overall improvements in detail with smoke and atmospherics, light glints, etc., throughout the film. I can't wait to check this out in HDR soon.