I understand your conerns, dr_bernie, but I have to say, seriously, if it's going to take you 2 or 3 days to optimize that scene in Carrara, then that's just further reinforcing my belief that Carrara needs a lot more done to it's modelling and workflow tools, and the render engine is something that can, and should, wait.  Especially when there's plugin technology to render in superior engines out there.

Keep in mind, that the Embree implimentation in C4D and Vray aren't major bullet points in either package.  It's almost a side-note in Vray.  Plus they don't work perfectly either.  You are restricted to use legacy GI methods with it.  The benefits are still good, of course, but even the pro implimentations have limitations and shortcomings, so it's highly unlikely to become the holy grail you are expecting for Carrara's user base.

I'm not against adding Embree, but as has been pointed out by a Carrara developer in an earlier post, it's not a simple thing, and Daz likely contracts out for all it's dev.  So that time and investment is better spent improving other aspects of the software for now.

---

Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.