I haven't tried all the programs mentioned above, but I like Rhino. I have RDS and like its procedural shaders, but its modeling paradigm is clunky and underpowered compared to Rhino. But Rhino is expensive (unless you're a student). You might want to look at Sculptor ProTools. It's only about $130. On the surface the interface looks like Rhino, but I don't know about the actual usage. Hey, Metacreations, if you're listening: don't kill RDS, just make its modeler better. There's a lot to like in that program, but the modeler isn't one of them. And, please keep it compatible with all my current plug-ins (I've got a fortune invested there).