I had p4 and never had p5, though I envied what i saw of it, at the time money was too tight to get it. I saved my lil pennies, and yes, got the pre-order of p6 and couldn't wait to get it in my hot little hands. In a nutshell.. P6 makes P4 look like a tinker toy. P6 has had some minor problems, mostly freezing up in the simulation in the cloth room. No render problems, and the freeze up was just twice probably because i was asking from it a hurculean task. you see, I am "learning" P6 as its a whole other entity from P4. I'm sure P6 groans at my mistakes :). On the whole though, things that did NOT work in P4 regularly work on P6. I no longer get the dread "obj not found" error i got constantly or the mid render freeze up and lockup of my whole computer that i did before. Nothing like P4 adding in just a shoe, and everything you just have worked on for hours goes buh bye with that obj error, yeesh. Even with the error, I loved P4, and love P6 even better... Though I'm stupid and still cant figure half of it out :)