Could you be more specific about your query?
There are many aspect about rendering that are of interest.
For one, are you talking the stock renderer in Creo or the optional rendering extention?
Next, what about rendering of animations and mechanism captures.
My biggest problem with the stock renderer is making the materials and lights work well together. Also making the room images effective.
I find that the shaded wth reflections to be more useful than PhotoRender. Somehow, it provides better image quality in real time.