I hope that in Rhino 6 is improved the kernel of intersection, so as to obtain the best result, for example, not only in the fillet, but also in the shelling (often fails when the faces of a volume have acute angles, or in cases of shell objects to tubular segments).
We wrote new curve and surface intersectors for V5 and have been fine tuning them as needed. The new Shelling code has brought additional changes.
This is a constantly evolving and improving process.