Poser 5 Python scripts with a user interface don't run on Mac OSX, because either Tkinter or Tk/Tcl is broken on OSX (no Poser fault).
Poser 6 Python scripts with a Poser 6 dialog style (wxPython graphics lib) should run as is on OSX.
Poser 7 adds a few things to Poser 6 that are definitely worthwhile. The render engine can use up to 4 GB of (virtual) memory, as opposted to the 2 GB of Poser 6 and earlier, and multithreaded rendering speeds things up a bit (or a lot, depending on the scene and the hardware)l. The Python script menu is a nice addition, so is IBL based lighting.

I'm not sure if the upgrade from Poser 5 to Poser 7 is worth it for the original poster (It was for me, but that's water under the bridge). A lot depends on what kind of scenes you want to do.

The $30 upgrade to Poser 6 is great value for money, for any Poser 5 user. The upgrade to Poser 7 will not be as cheap, and might not be as good a deal. Again, that depends on hardware and (intended) Poser usage.

The pen is mightier than the sword. But if you literally want to have some impact, use a typewriter

My gallery   My freestuff