"...but it seems that it was a huge leap in stability and functionality..." A huge leap backwards, IMO. And all SR4 did for me was slow P5 down even more and create new problems with the P4 renderer. But heck, go for it if you want to play with the new flashy stuff and don't populate your scenes with more than a few characters. But don't expect much improvement over P4/PP, it's essentially the same program; just slower and clunkier, IMO.