I would not call it a complete disaster, but there are some clear functional regressions compared to NX2, most obvious is the lack of U point technology (which remains in my view the most revolutionary image edition tool since layers).
It is reasonably responsive on my Mac Pro 2013 and colours seems as nice as they used to, but I will not make it my converter of choice.
I was unfamiliar with control points so I went to the Nikon website to look at how it works. I recommended something similar to the Raw Therapee forum last year, which did not go anywhere for the complexity (I guess) of getting it to work with the rest of the existing code. The idea was in 2 parts.
-You right click a point on your image to make a control point on your curves graph. This lets you move the area you see as a problem rather than grabbing the curve, hoping you got a close point.
-you right click to get a color wheel in a circle around the point for very fine color vector adjustments. That matches the RT logo.
Somebody should still work that in. The whole thing of all these control panel type adjustments at the side, in all these programs, show a primitive way of working with the image. More thought should go into a system for adjusting at the image.