A few extra bucks?  You mean a few hundred, maybe.  I have Poser, and I love it.  I don't see these plug-ins that bring it anywhere near Poser's price.  Hopefully the SDK will bring some forward.  Hmmm... how much would you pay for working softbodies?  Fluids?  Atmospheres?

Poser has a $50 plug-in for physics, and many other shaders and such are commercially available.  I can see complaining about the lack of certain features, but I think this is a very good free program, even if end up becoming someone's expensive new hobby.