I believe on ordinary functions P5 does run slower than Poser 4 with PP, but the frist service release pack seems to have helped a great deal with that. I'm still not used to the lag and I have a Pentium 4 with 526 megs ram, plus a video card with 128 megs ram memory running Windows XP home edition. In my opinion, where P5 shines is the Firefly Rendering Engine. The results I've gotten with it are much more realistic looking and more in line with the results I've achieved with over 3D software. That has made it worth the upgrade for me, not having to export to get a good render.