After using RPR 1.7.212 for about a month now i think that it does a fantastic job. Even interior scenes with a lot of indirect light render blazing fast.
The same is true for instanced objects at large scale - it's just gorgeous.
But while in small scenes the interactive viewport starts immediately and works pretty well and stable, even if you change and tweak materials or environment lighting, it takes some time (about 30-60 sec.) to start in larger scenes with a lot of objects and textures. As well, the viewport crashes then when i change something in the scene.
To me this seems to be the only really counting weak point of RPR at the moment.
WIN 10 PRO
ASUS VEGA 64