Jumping straight to P6 from P4PP, and having gotten used to using C4D for rendering, I initially gave Firefly only a few faint-hearted attempts.

At first, I got these bizarre empty areas, especially around the eyes or other areas of high detail, but then I noticed those went away when I turned off 3D Motion Blur (does that really work at all, or is it just my particular models and/or scenes?).

Gave it a couple more tries, but wound up crashing alot, until I saw the tip elsewhere about lowering the bucket size. Finally got a complete render but still didn't think it was any better than P4 Renderer or C4D.

BUT....

then I tried the IBL lights with Ambient Occlusion plus two to four strategically placed spotlights, and was stunned to see a huge upward leap in the realism of my characters (realism being an objective of MINE anyway).

So I, for one, am going to try to learn how to make Firefly work. Key obstacles that remain for me include --

(1) how to save IBL plus spotlight sets to the library, or at least a PZ3 template, so I don't have to reconstruct them every time

(2) figure out whether and how to successfully incorporate (3D?) motion blur for my animations

(3) figure out optimal bucket size (I currently default to 16)

(4) whether I can get a hybrid between the regular shadow mapping (shadows a little too fuzzy for my scenes) and raytracing (shadows a little too sharp-edged for my scenes).

So I'm still trying to tweak and learn, and hold out hope that Firefly will work for me.

Best of luck to all who search for the perfect renders!