Carrara is a fantastic program, the renderer is amazing as are the plant editor and the hundreds of objects and presets that come with the content CD but, Jack's right, the atmosphere engine is shite(***), like a slightly better Bryce effort.
I mostly solely work with TG2, Carrara 6 and Adobe CS2. All I need really. Carrara is an all-in-one 3D package that I couldn't do without now, it has everything and the UI is very intuitive, (not to mention the default 3d view control system is identical to TG2).
*** It isn't really shite, more, I'm shite with it!
For modelling objects and making/rendering indoor scenes nothing comes close but, for realistic landscape scenes, you really need to put the work in to get the visual payback from Carrara, I find.