I have two i7 systems, and neither ppro nor poser 7 will use more then 4 threads (you can open task manager to check this, if all 8 graphs are not at 95-100% then its not using them)

I also use Vue and XSI and both use all 8 and i get like 15-20% more performance as compared to 4 which is pretty good IMO.

Hopefully the next versions of poser will add support for this...