The new release candidate is out now, I've tried Paq's superball and it seems to render fine as far as I can tell. But I don't have a lot of experience in this area so I hope other people with Octane license will jump to testing. The test cylinder shows no seams.

As for the flat polygon test - it mostly looks ok, there's some weird "shadow" creeping up from some angles, I don't know if this is related to vertex normals or the lighting system or what. But at least the polygon is shaded now.