No it's just 60FPS. The scene is rendered at 60fps and the image is split 960x1080 which produces the view for both eyes.
But it's not rendering at 120FPS though, it's still one image being rendered at 60fps, the scene is being displayed twice for each eye and then output onto a single screen (with the Rift) and using the attached lenses that splits your vision so each eye only sees the specific side of the frame.
Not sure if I'm misunderstanding but yeah, it doesn't 'double' the FPS, it actually "sort of" doubles the rendering, but not really. If you take the lenses off of your DK2, there is actually two viewpoints of the game being rendered at the same time (why we see those 'double view' videos all the time), like having two instances of the game running side by side, it's why in games like ED or AC you have to drop some of the more intensive stuff down (shaders, etc .. ) because most GPUs have issue handling that much.
I think I might have just said what you said though, lol. Just a bit of clarification.
And even then, at 60FPS, that isn't even a 'minimum' for me, you still get blur, you still get a delay and such, the DK2 can render at 75FPS and that should be the BARE minimum IMO (Oculus is shooting for 90 in CV1 I believe). The higher the better because the less motion sickness you will get. Even at 75FPS you get some judder here and there when rendering becomes too much in some sections of games and you notice it so going higher and dropping to something that is 'barely noticeable' is always preferred over being at the minimum and dropping to something that will drop you out of immersion.
Either way, games not designed for/around the Rift sometimes have difficulties with scaling speed and movement. GTA V in FP seems fast as shit! It might be pretty difficult to play for long periods of time because of the movement (for a lot of people, not all). I know HL2 looks great, but it's something I can't really play all that long while ED or AC I can play for longer because of the 'sitting' experience.
But I can't wait for the PC version, modded DK2 support or not, walking on top of a train while blaring through the countryside is going to be amazing. just looking around and down and able to 'fall off' will be something special. And the underwater sections? Holy shit. It's funny, because the 'simple' stuff is always the stuff that amazes me the most when it comes to VR, just docking in ED or slowing down and leaning out to look at the road in AC are some of my favorite moments.
First game I'll ever TRIPLE DIP for. And worth every penny.