Carrara's Sky Lighting and Indirect Lighting are untolerably slow, to the point of being useless for practical purposes.

I did a render of this scene with skylight and AO only. Chandeliers hanging from the ceiling have transparencies in their textures.

http://www.daz3d.com/baroque-grandeur

The render took 3 days on a pro level machine (Dual Xeon @2.6MHZ, 16 threads, 24GB DDR3 RAM). To Carrara's credit though I should add that the render finished without crashing. But 3 days? Most definitely useless.

The solution, as I have stated in several other threads, is this:

http://software.intel.com/en-us/articles/embree-photo-realistic-ray-tracing-kernels

which gives this kind of results in Cinema4D:

http://www.youtube.com/watch?v=rJd-WEtkg-Q

Instead of implementing the state-of-the-art technology that Embree is, Carrara 8.5 is gratifying us with a laughable technology from the 1990's called 'Fast Mipmap', which belongs in low-level game engines to speed-up real-time display drawing, not in pro level 3D apps as a mean of speeding-up the renderer.