Right after I installed SR3 my render times deteriorated from about 3-5 minutes to 30-40 minutes.  Naturally, I assumed it was due to SR3. 

I was wrong. 

My problem had to due with a hair prop which I discovered by trial and error.  Once I deleted the hair prop by render times went back to the normal 3-5 minutes.  I wish I knew the name of the prop, but I changed it when I loaded it and my runtimes are too much of a mess to search.  When I come across it again, I will know it.

In the process of researching I got the following input from SmithMicro
 - SR3 should facilitate faster loading and about the same render time.  That is my experience.
 - Number of runtimes loaded to the library bar should have no impact on render time.  Impact on load time is an open question.  This has been my experience also.
 - Increasing the render threads to match the number of cores was a big help.
 - Irradiance caching will have no effect on Poser 7 render time.  Apparently, it is related to Poser Pro render time.