After having used my DK2 for a number of hours in SL, I _really_ want Hydra/Stem (Hydra v2 basically) http://sixense.com/ intergration in world, so I can actually wave, point and generally use my hands in world. Would help a heap with the immersion.
Not to mentio there are a multitude of hand positional tracking devices coming out of the wood work due to VR now, so there may be a demand for them in the future.
But I can see this, we're going to loose a lot of people into VR when they use SL. Its surprisgly immersive.