It's a wonderful toy! Amusing, easy to use and gives good results for the low price. Firefly renderer (P5) alone is worth the money of the software. Raytraced reflections and refractions, volumetric light, depth of field, motion blur, depth cue... if you get to learn to use those well, you can get amazing results without needing any postwork. The material room has enormous potential. The drawbacks are: 1- definitely scarce manuals and documentation (but there are tons of good free tutorials around) and 2- possible crashes if the scene contains some improper geometry (most products sold around are good, but there are some hair packages that have many errors like intersecting polygons, stray vertexes and so on... those can cause most of the renderer's crashes). Buying P4 now is like buying a car produced ten years ago. If you have it and it still works, keep it. If you go for something new... definitely get P5.