MetaStream 3.0 is created as a new 3D file format to show streaming 3D objects over the Internet. With the free MetaStream plug-in, users can interact with 3D Web graphics in real time by zooming, panning or rotating objects within a Web browser. MetaStream also scales objects in real time to match the performance of a user's system. And with its smart compression technology, MetaStream handles 3D geometry and texture information so files that can be delivered more quickly to every user's machine.
So I wouldn't think you'd be too lost without it - unless you do a lot of 3D graphics work.