I'm thinking that, as well. Have asked on the steamvr forum. Seems to be spammed with general usage questions, though. Little dev-talk.
We'll see. If it's not recommended to extend SimpleApplication like that, I'd like as far as possible to avoid it. Besides, the GuiNode might work differently with the new arcitecture.
That should actually be out of bounds, what isn't rendered by the shader. I expect that with correct distortion, they would have more of an angle. I switched the default black to red to make sure what was happening there.
If it works anything like the cardboard (I am assuming it does), the getEyePose matrix should return the correct offset. So yes, the cameras should be separated, but I don't think we have to create the vector ourselves.