With 28.0.92 available, I finally decided to also give it a try. Its main task is DVD upscaling (as >95% of my movies are on DVD, as *.iso on my server). With madVR, I had found a set of settings, organized in profiles, that would work very good with this SD content, while also taking care of the few BDs (also *.iso), and even fewer *.mkv and *.mp4.
I started with one of my worst case DVDs for upscaling (James Bond - The Spy Who Loved Me, original release, when there were still CRT TVs, no HDMI, but SCART etc.). And I must say, even with the highest scaling settings applied, it currently doesn't get close enough to madVR.
I have included two screenshots for comparison (cropped the black bars because of the file size limitations in the forum). Especially focus on the straight and high contrast lines on the Esprit's roof, windscreen frame, and door. Also, faces, Bond's right arm, and several other places. Overall, the picture doesn't look that natural and smooth, compared with madVR. In motion, it gets even worse. At first it looked awfully bad, but I found that, although I had selected OK after changing all the JRVR scaling settings, they were gone. I had to redo them, select Apply, and then OK, and finally, the high-end scaling selection persisted. Then, it was definitely better as before. But, currently, it's not working for me, DVD upscaling is too bad (compared to madVR), unfortunately.