I don't know what it is.  Maybe it's clean living or something; but, I've had not one issue with 4.5 other than they way they hosed the locations of the genesis shaping morphs for the head and face.  Integration with reality has been flawless.  Then when using Lux, I can go cpu only or hybrid and still have no issues at all.  My one issue with lux is that if you close it out or it crashes while a network render is going on; sometimes the slaves don't reset.  After building this big(ger) computer; my sole issue is why I'm not getting the same render speed as other folks are getting with mesh lights.  Fastest I've had it going so far is 350k s/s with an ibl.  Is it how I've got my materials set up?  Is it lighting?  It's it a ram issue?  I usually get about 150k s/s with an ibl and around 70k s/s with mesh lights.  If I try to do a really busy ambitious scene; I'm back down to 10-15k s/s.