I've noticed that filleting is a problem in all the 3D modelling programs I've tried. Although I've not really tried any of those big CAD applications like SoldWorks. But those things look far too cumbersome for what I want to do.

Despite MoI having some filleting problems, it can still manage to fillet things more reliably and easily than all the other 3D modellers I've tried. Then there's the fact that MoI feels so damn nice to use.