Personally, if I were in your shoes, I'd wait until Poser 6 comes out (and check to make sure there are no massive problems inherent in it) before upgrading from Poser 4. OTOH, I happily admit that Poser 5 on OSX does work well enough for me (OS 10.3.8 on a dual G5 box), though IMHO you'll need a somewhat hefty bit of kit to run it without seeing the beachball o' busyness all the time. Poser 5 on my old 1.2 G4 Cube tended to bog down once in awhile. /P