It's odd that this is a big deal, it has been around for some time. I have seen it in a lab. It is not actually invisible to the eye, it is wavelength sensitive, so it only has the negative refraction value for one wavelength (and it is not a visible wavelength). Keep in mind that it actually is visible even in its set wavelength because it has a negative refraction value; only when paired with an equal positive wavelength value does it become invisible at that wavelength.

This just may get me laid.