I finally found time to install and test LR RC 4.4 on some raw files.
I looked at half a dozen problem images I knew had excessive color bleeding. The color bleeding is eliminated in larger pixel areas and greatly reduced in very sparse pixel areas. I do not think large prints will exhibit pixel bleeding artifacts. I have to send some files off for large prints though.
In another image a blurred vertical line I had previously thought to be an artifact in high contrast sign was crisp. This line is probably about 10 pixels wide.
The improvement is dramatic. The LR sharpening response is quite different too.
When I revisited some of my 18/2 XF images, I noticed the longitudinal chromatic aberation seemed reduced. Right now I think some of the vertical artifacts that resembled CA I sometimes saw at the frame edges (and removed with the Lens Correction module) were actually caused by errors in ACR. I have to look at more examples to be sure.
Anyway, I am very happy with Adobe's new XTrans rendering.