I tend to run everything I buy through a runtime repair program first - it converts the rsr's and corrects any little errors. It can be surprising how many get through the net sometimes, so I'm happy to do this and have been doing it long enough that I wasn't affected by the drop of rsr support - it always struck be as odd that they should drop it though, I mean, what's the benefit of reducing function?.

If I remember, I think that Poser began using png format with Pro Pack (the one that expanded Poser 4). Of course, back then, Poser would create the rsr for you, I think that content creators today might find it a bit of a hastle to make them.

Once upon a time though, and I think still with Poser 4 content (I remember the old DAZ dragon did this), rsr's were used for geometry. It could cause a few problems too.