My experience is that files with pc style paths will open fine on the mac, only it takes longer time for Poser to locate the files.

Also, you can hook your pc up to your mac to transfer stuff directly. I have both a mac and a pc and I do that often.  As mentioned before, assuming you're using Poser 5 or later, the only real problem are rsr-files instead of png's for thumbnails.

At this page you can see how you can network mac&pc:

joelandfaith.com/computer/mac/macfilesharing.html