I have tried Moi3D (very cool and promising software), and i have some remarks:

Some tools like a "zoomed window" would be usefull when connecting lines/curves. (after some hours of deleting/connecting curves, i figured i got some curves badly connected, had to zoom manually the "scramble zone" to correct it)

When Lofting/Sweeping some color could be used to show outer/inner sides (i means from a surface normal point of view).
after exporting to .3ds, i needed to swap some surface normals (hopefully a MoI NURB is translated into a 3DS Node/Object).

For Lofting/Sweeping, since the curve extremity selected is meaningfull, perhaps a hotkey (middle mouse click) when on a curve to swap the extremity selected. thus it would avoid to cancel the lofting/sweeping and re-start another time.

I am awaiting a lot surfacing capabilities with networks of curves :)