I tried all sorts of test scenes with OptiX and it was night and day compared to P12. The render presets are great to test your speed and quality with, and are very convenient. DoF also was fixed.

With HDRI I spent the money on the HDRI script Ken1171 put to the marketplace here, for real HDRI without need for a dome or jpgs. It really made a noticeable difference in how a scene is lit. Of course, we need to keep in mind that not all HDRI images are created equal--in my opinion, still too many low quality ones are used OR used with outdated additional lights. But that's an entirely different rant.