Windows 10 beta tester running on fractal define 3 with Asus X99 workstation 32 Gb ram. Poser pro 2014 with no problem since midlle builds.

Update (if you do it properly ) is faultless - if you have any worries use windows backup and restore. in the Released version of windows 10 there is a facility to roll back windows 10 to 7 but nuking the drive and then doing a restore from a system image will do the trick.  make sure you have an emergency disk.

Poser is roughly the same rendering speed with firefly Runtimes and poser is slightly faster ( roughly the same as windows 8.1)

Windows 10 does need tuning to get rid of all the privacy tabs and stuff - there are good tuning guides on the web for this. you can fiddle with the update settings in Win 10 pro  to give you some control.Ive found it pretty stable and a worthwhile upgrade.