I switch back and forth between MoI and Rhino all the time when I work ... I prefer to do my 3d stuff with MoI and notes and dimensions and such with Rhino 2d.

And there are times when Rhino will work with 3d stuff that MoI has trouble with (though that is very rare).

I have T-Splines but for my work do not use it often ... I am pretty sure that after using T-Splines you have to convert back to nurbs before it can be seen properly in MoI.

cheers,
eric