P5X is really well done, especially when it comes to stabilty. For me it almost never crashes, I got pretty good at crashing P4PP. Being able to have multiple runtimes is fantastic - you can just leave your current runtime where it is and not have to transfer all those files over to P5. The big down side for me is that P5X is really slow, especially using the cloth and hair simulations. It's also kinda shocking that the new Firefly render engine which was written for the Mac sometimes runs close to 50% slower then PC firefly (depending on content). Also some P4 content (which is still most of the market) has to be tweaked in the new material editor but the new ME is really kinda cool - not like Bryce or Vue but much better then P4 offers. While it now reads PC resources directly, it still doesn't read the PC thumbnail preview so you still need to use Mac Converter.