I tend to like FireFly renders a bit better then Poser4 renders...I don't know enough technically to say what but it just seems as if the result looks richer to me and there are some materials available in Poser 5 that simply will not render with anything else other than FireFly within Poser 5. I don't believe you can get actual reflections, for example, with Poser 4. I don't know if I've gotten used to it or the latest patch helped, but it seems as if the renders are not taking as long as they used to. It all depends on what you want. I would not buy Poser 5 because of FireFly renders, but, having Poser 5, I certainly want to take advantage of the benefits that it provides.