Nyghtfall said: "What I find particularly noticeable about BB's Superfly render is the lack of shadow artifacts where the ceiling meets the wall above the windows. Unless SM has finally solved that problem with Firefly, they may have finally provided a solution with Superfly."

What you're seeing here are unbiased renders - a totally different animal. The shadow artifacts you're referring to are a common problem with interior scenes rendered with a biased renderer (like Firefly). They are a result of the way biased rendering works: to save time it takes a predetermined number of samples from the scene, measures the light at those points, and interpolates the light in between them, essentially guessing. Usually the guessing works well enough and the time savings are huge, but in tricky areas that interpolation process can yield screwy results which show up as shadowy and over-bright splotches in the render. More samples closer together can obviously help, but that takes longer, so the better biased renderers try to find more efficient ways of taking the samples and more sophisticated ways of processing them.

With an unbiased renderer (like Cycles) it doesn't interpolate anything, it just keeps firing rays into the scene until, if given enough time, it has sampled every single pixel. If you stop it before the process is complete (either by hitting the stop button or by limiting the total number of rays it should fire) you get a grainy image - the grain is the pixels it hasn't had a chance to do properly yet.

The trade-off is time. Guessing is quicker than firing lots of rays. By way of example, the unbiased MODO render I posted above took 35 minutes and it was still grainy (that was using modo's preview render set to full size). The same scene using modo's normal biased renderer took just 50-something seconds, but it has some splotchies around the edge of the ceiling. It typically takes quite a bit of skill, experience, guile, cunning and trickery to get a biased renderer to deliver the result you want (to help it guess correctly, if you like), whereas an unbiased renderer doesn't get involved in all that, it just needs fast hardware and time.