In the very likely case that you're unable to take advantage of these yourself, Digital Foundry has provided some impressions of what they're like. You can also check out the video below for a comparison of the PS4 and PC (with Ultra textures) versions.
Expectedly, it's very pretty when running the game at Ultra. However, it's not the kind of leap over High that you might be hoping for, particularly because the most-improved areas are hard to notice while playing the game in a normal manner. "For the most part, we found that the high setting--in itself placing a significant video RAM requirement on the user--offers the bulk of the ultra experience," writes Digital Foundry.