I have Ray Dream 5.5 running on a blue & white 300mhz G3 Mac and don't find it to be slow at all (it was a drag on my previous 75mhz performa though). I can't say that I find it easy to use, but I'm new to 3d, so almost anything would be hard for me. If you're running on one of the superfast Pentiums and using a 3D card it should be about as fast as it is on the Mac, I would think...