I've been using Carrara on a G3/266 (at home) and a G4/450 (at work) since just before Christmas. It does have a few bugs, but none of them are the kind that make it unusable; they're just annoyances that I got into the habit of working around pretty quickly. As far as features go, it's virtually identical to RDS 5.5. Despite the name change, it's really RDS 6.0, with a funkier interface; if you know Ray Dream, you'll know Carrara in about an hour. The interface, while it's a little heavy-handed in the graphic department, really is a work of art; the multiple "rooms" of the interface really do create a smooth and efficient workflow. For the 15-20 projects I've completed in Carrara so far, I've found myself finishing them in about half the time they took in Ray Dream -- not because of the speed of the renderer, although that's faster too, but because the workflow is so much more efficient.