I switched to Carrara as my main renderer a couple of years ago as well and I love it. The transition from Bryce wasn't hard for me because parts of the Carrara interface and the terrain and tree editors are similar to Bryce's. I use the modelers occasionally but still do most of my modeling in Wings3D and Hexagon. I really enjoy the surface replicators which allow you to put tens of thousands of trees, rocks, buildings, people etc. into your scenes, and the displacement mapping makes it possible to add tremendous amounts of detail to a model.
Carrara IMO is like Bryce on steroids!