i think that the human behavior aspect noted so far is correct.  if you don't ask them, people who are happy with p7 are just going to render and be happy with it.  if you're frustrated, you're likely to come to the forums and curse the software and its makers and hope that someone has a solution.

when i started a thread specifically asking whether p7 was a more stable and powerfull renderer, i got lots of positive responses and maybe one negative one.  but if you look at all the recent threads, all you see are complaints.   personally, i have a fairly simple scene that's crashing p6 in a very annoying way (permanent hang- just  leaves a blank render screen, says it's rendering, and takes up a whole processor and 1.1 gigs of ram).  i'm really hoping p7 will like it better (i'll revisit it when i get it).