Well, MoI's filleting has up to G 3's, but if the "look" of it is not what you thought you wanted, you have to change the underlying "staight parts" to acheive the look. In other words, you have to know what the underlying straight part should be modeled like to get the "look" after the curvature is applied.

Like using T-Splines. Can you model a bunch of squares together to make the output for a cool, curved surface shape after you apply smoothing? It would be difficult.

BTW: Viacad is working on the next version which should have the sub to nurbs in it! I'm not clear yet whether it will be a "shark only" tool, or if it will be in the pro version also....