Just got to install P13 (finally - mac user).  First quick impressions:

This was a simple test.  A P12 file opened in P13 with nothing changed then simply rendered at whatever it was setup for before (CPU High per ghostship's settings with 18 cores).  I didn't stopwatch anything.  But before when using CPU in P12 I would decrease the bucket size so that more cores could be working the hard parts at the same time (hair, usually).  In P13, I saw only one "render box" and not one for each core.  So it *seemed* slower.  But I don't know how P13 works with a P12 file.  I switch to the GPU - Radeon Pro 64 (iMac Pro) and it was *way* better than GPU on a Mac had ever been (for realistic renders, GPU used to be unusable). 

I can see the new renderer is going to require a step-up in mats and probably more geometry.  The hair ribbons are obvious as such.  A better transmap would help, I think.  I loved the way the GPU just smashed through the hair shader like it was nothing more than an image map on a plane :D

Also, on my Mac, post render stuff would crash Poser.  Now, it seems rock solid.  The de-noiser rules!

There are all sorts of little improvements I noticed even just installing, opening a file, and rendering.  I haven't even started messing with it. 

Well done, Poser team! 

Can't wait for the next-gen figures.

Oh, this is La Femme if it's not obvious :p