Hmm I don't know what particle systems are (haven't used Vue). For a physics system they could use the engine used by Half-Life 2 and Painkiller; you can buy it, it's used in multiple games and works just fine. Then they wouldn't have to develop it themselves, just integrate it into Bryce for animations as a system of determining key frames. I don't ask for something as powerful as Vue (though I wouldn't mind it lol), but what I do ask is my money's worth. If I have Bryce5, there are so few new features in Bryce5.5 that it's not worth $70. As for the upgraded import feature, there are ways to work around not having it (such as rendering in Poser, full render and mask and then integrating in postwork), or using Photoshop or Paint Shop Pro to hand-draw hair, which is the only thing that won't export from Poser properly, always and annoyingly excepting animations, but that's not fixed in 5.5 The pricing for the actual program is fine, in fact it's great for what you get. But they are way overpricing the upgrade since you get very very little new stuff.