Just a short mention, in case anyones else runs into this: as it appears, some of the problem P6 had with rendering reflections and refractions have been solved, but bump maps still aren't handled correctly. I tried a recent P5 scene in P6 and got very noisy reflections and refractions, but only for those parts with bump maps applied. Disabling the bump maps apparently solved the problem, and it didn't occur with displacement maps, either. Oh, and increasing the sample rate didn't seem to help. I haven't yet tried playing with the shading rate though, which was already at 0.2, or the shadow bias. At the moment, changing bumps into displacements seems to be fair enough as a workaround for me.

-- I'm not mad at you, just Westphalian.