Import - *.wrl, *.dwg (3D data), pdf underlay
Export - 3D pdf, *.dwg, *.bip (for us Alibre users :-) )

Other than these I don't really have a "top 5." Even these are a "would be nice" feature and not something I would quit using MoI over.

Stuff that I would have in a top 5 you have already hinted at working on (mainly UI stuff).

Thanks!