I bought these knowing that the quality may be suspect based on other reviews, but it's a new style for me, so I would rather dislike the style at under $20 than a higher price point.
Positives are the look, the feel on my head (i.e. the bayonet arms are comfortable and stay in place), and knowing that my head needs 57mm sunglasses.
The only negative is that the left lens does move in the frame when I wipe them, so I am assuming that in time it'll pop out.
Also, I can see my eyes through the lenses, so no gawking at people in these with anonymity.