Biggest improvement you will probably like is 64-bit (done if I read the Bug Tracker correctly), followed by multi-threading of the most CPU instensive calculations, network rendering improvements, COLLADA import and export tweaks, and I could swear I saw IES lights as completed, again, if I read the bug tracker correctly. If true, improved lights will help get you to more realistic scenes as I always thought the color is wonky in many Carrara renders. I don't know if it's the artist or the product, but it's happened enough over the years to make me think it's the software or a combination of user and software going astray.