This effect struck me as inconvenient:
Their analysis also revealed another surprise: a person trying to look out of the cloak would effectively be faced with a mirror in every direction. If you can imagine Harry Potter’s own invisibility cloak working this way, and Harry turning on his flashlight to see, its light would shine right back at him, no matter where he pointed it.
Back to the drawing board, I suppose. Professor Greenleaf also cautioned:
“We should also keep in mind that, given the current technology, when we talk about invisibility, we’re talking only about being invisible at just a narrow range of wavelengths. For example, an object could be rendered invisible at just a specific wavelength of red; it would be visible in nearly every other color.”