Previously all I had ever heard the big selling point with MVS was that if you used T-Mobile (because of their UMA package) you could save money with reducing voice recurring charges by lowering your overall minutes. However, that was a problem as depending on your area T-Mobile may or may not have been the carrier of choice for your employees or company.
Now that RIM has opened up MVS to take advantage of SIP, and allowing itself to move off of strictly Cisco PBX branded hardware (a problem for us). In addition, RIM did not make wi-fi ubiquitous throughout all their handsets. Now that even CDMA handsets will include wi-fi, the choices are much more open, and could compel businesses with especially international needs to take advantage of this version of MVS (Mobile Voice System)