Sorry to drag this one out again, but it does show that rendering large and reducing will hide the grain a lot. This was actually quite a low rpp setting (and was still an 'overnight' render time). In fact, I think the method can provide some photorealism to 3D pics by adding in a bit of softness and 'film grain'. The pic also shows that careful composition and not getting too close to mesh models can hide the mesh facetting under True Ambience successfully enough to use the process for making images using 'Poser' figures.