Bryce 5 is nice, I used 4 for about a year and just switched to 5 recently, you can almost completely customize your rendering with alot to make your scenes look better, up to 256 rays per pixel too,lets see, metaballs, tho not exactly a huge deal are still a great idea, they're just balls that melt together or repel each other, really great for making organic shapes the textures melt together just as smooth as the balls do too. and the tree lab is great, not perfect, but its really nice to have. and ok, so you get slower renders, but what you get from it is worth it most of the time, anyway, what i say is, Bryce 5, worth buying the program? no. the upgrade? yes.