I have P5 on my underpowered Win98 laptop and haven't had problems. Of course, the most ambitious thing I've done is some fun experimentation with changing settings on the built-in hair styles. I still do my multi-figure animations in P4ProPack on my Mac - but I get SO irritated with the lack of nested dial groups and library folders and really miss P5's professional materials handling. So I'll be at the head of the line for the Mac version of P5. Of course, I'll probably also buy Daz Studio.