[bl]

"[I]t's a bit of a stretch to say that they've rewritten the rules of refraction."

Indeed. It appears more akin to the situation we have with classical and quantum mechanics: classical (Newtonian) mechanics fairly accurately describe the behavior of macroscopic objects at relatively slow velocities. We acknowledge that the system is not valid outside of that range. But since that range encompasses the bulk of our everyday, practical experience, classical mechanics are exceedingly useful.

Classical optics are not suddenly outdated with these discoveries. Snell's law and the lens-maker's formula are just as relevant as they were yesterday. We just need to add a few more terms to the equation if we etch a gradient of nano-scale resonators to the surface of our optical element. (Boy, do I feel like Geordi in Star Trek reading that last sentence aloud.)

Negative index of refraction materials are not quite new: wikipedia indicates that they are already being used in commercially-available products (http://en.wikipedia.org/wiki/Negative_index_metamaterials). For me, the most exciting application is creating a lens that circumvents the diffraction limit that limits optical imaging resolution. Right now, the most sophisticated, expensive microscope objective lenses can just barely resolve sub-cellular structures only under very particular conditions (i.e., not alive). A diffraction-unlimited "superlens" made out of this stuff could enable us to see even smaller objects under physiological conditions. It would be fantastic if we could capture the release of individual neurotransmitter vesicles at a diseased synapse, for example.

Besides negative index materials, there are a whole class of non-linear optics (http://en.wikipedia.org/wiki/Nonlinear_optics) that allow engineers to do all sorts of funky things in their instruments, like doubling the light frequency or self-focusing.