Just spring for the upgrade. You can still continue using Poser 4. One key thing for me is that Poser 5 has fixed the crosstalk problem, so I can have multiple Mike's with different morphs applied without having to jump through the hoops of the work around. Because I want the option to work with Vue D'Esprit Mover 4 and Lightwave, I continue to use P4 PP primarily to give me that option, but as I develop projects that don't require that functionality, I am using P5 more.