I have Poser 7, Poser 8 and poserpro 2010 on the same laptop and yes they all worked fine with each other in the same applications directory (i use a Mac)

i used to use poser 7 to set up my scene - save it and then open it in either Poser 8 or poser pro 2010 to render because i use reflections and such and i love the render engine on 8 and 2010.

I did a sidegrade from poser 8 to poserpro 2010 and its the full version.