Rhino has always been associated with failing fillets. The only reliable way to make high quality (G1 or better) fillets is using the XNurbs plugin. On the other hand, Rhino SubD objects always have perfect fillets. It seems possible to make reliable, high quality NURBS fillets with the help of the SubD kernel.
Andrew, you who is digging up tons of different software packages should know that this is not just a burden Rhino has to carry.
i read somewhere not too long ago that it is being considered integrating subd match to nurb if i can remember correct, if not it might be a good idea anyway.
also something native like x nurbs would be lovely for those working with nurbs.