All versions ( at least since my first version 1.x ) of visual mill open native Rhino files. Those two programs are about all I have used for over two years.
The new VM5 actually uses licensed Rhino code for geometry creation internally. Mecsoft and McNeel seem to have a very close working relationship.
Take care,
Phill Pittman
www.masterwerkes.com digicarve@verizon.net