SR3 has made my render times go from 1-2 hours to 24+ hours (I ended up just doing a Ctrl-Alt-Del after an overnight render would not even finish) ---wow.  SR3 seems completely worthless to me.  Maybe some are not having this problem, but it has been a royal pain in the butt for me, I really suggest not installing it. 
     I have read another thread here where people are saying -the developers can't test on every hardware config. etc....,  and other excuses, possible workarounds, and other nonsense, but this is unacceptable. 
     I installed SR3, reinstalled SR3, uninstalled Poser, did a clean install, reinstalled SR3, defragged, increased my VM, blah blah blah.  I spent nearly 2 whole days trying to figure out what the problem was- is it my recent windows update, my graphics card update, and was about to do a reformat- thankfully I did not.  SR3 is worthless, don't do it. 
     I am back to 2.1, thank god I saved it and the render time is humming along nicely again.  Just say no to SR3.