I started with Bryce 3 and all I can say is that B5 is quite a bit nicer. Same feel to the interface, trees added, lightlab, metaballs and a much better render engine that has the speed settings you are used to and the quality settings for beefier computers. Skyz and materials room seem to be pretty much the same. Considering the price on ebay, I'd say its well worth the upgrade for ya.