It seems they are pushing this as new. Though Nvidia's own Quadro cards have had this for years even ones which were based on GeForce 4 chips (look at ones with 3pin stereo connector on http://en.wikipedia.org/wiki/Nvidia_Quadro).
Nvidia have always made it so that only expensive Quadro cards can do Quad Buffered stereo which is what is needed to do the rendering properly (a double buffer for each eye). IR-glasses have been around for several years (http://reald-corporate.com/scientific/crystaleyes.asp) and operate by pluging a transmitter into the 3pin port onto a quadro card (or their are other methods such as blue-line stereo). Shutter glasses in the past have been too expensive ($500-1000) though mass-adoption should bring that down.
Stereo also works under OpenGL on Linux so I don't see the problem with that.
The only thing that seems new is that Nvidia are pushing it, it may end up on consumer cards and the stereo conversion of existing games.