The disconnected hand / floating gun thing still bugs me a bit.
When you are in the demo, it doesn't bother you at all. Having a forearm that isn't mimicking what your forearm is doing in real life is way more bothersome.
These floating hands work in VR well because - and this is really hard to explain to anybody who hasn't tried VR or, worse, has tried something like Kinect or Move on a normal TV which does the exact opposite - your hand appears to be in space where your brain reports it is. That's called
proprioception, our body parts have the ability to report to our brains where they are in relation to our head. That's why police tell you to close your eyes, tilt your head back, and touch your nose with your fingers when you are going through a sobriety test - alcohol affects our proprioception. Drunk people's bodies report back poorly, which is part of the reason they stumble when walking.
In a sober person, we have strong proprioception in our hands and fingers. Our bodies know where they are in space, even when we don't see them, to a pretty high degree. Obviously our eyes have the highest proprioception in our body. But in VR, unlike kinect or the wii or whatever, those floating hands seem so right because our eyes see them in the correct position our proprioception reports them to be. That cumulative feedback - multiple systems in our body aligning correctly - helps fool us into believing what we see is real, even if our conscious mind knows it is not.