Ran into a curious case where if you have two geometricly identical overlapping bots where one is smooth and one is not, the raytrace will be wrong. Most disturbing is that the bug even occurs if the overlap is from a negative space object (e.g. BoT used in a subtraction).
The problem can be seen with a simple sphere and a box used to cut the bottom half of the sphere off. Turn the sphere into an BoT, create a region for the bottom half that intersects the box with a usual unsmoothed BoT sphere, and create a region for the top half that subtracts the box from the *smoothed* BoT sphere.
The result should be a unsmooth BoT base to the sphere and a smoothed top portion. The result is an interleaved smooth/unsmoothing throughout.