I purchased the Permit with 580G silver mirror tint lenses a couple of months back and have overall been very impressed. I had heard plenty of good things about the Costa products - and have had other polarized glasses with poly lenses before (smith/spy). Those sunglasses were nice, and I still use them occasionally - especially when doing active things where there is more risk of damage than normal.
That said, what was important to me in purchasing my next pair of glasses was 1) fit, 2) optics quality 3)look 4)durability (I'm very careful with my gear - so this sometimes takes a backseat when looking at priorities - not to say they aren't durable.)
First impressions were good - I like the weight/feel/construction of the sunglasses - is the glass heavier than poly - sure, a little. Do I notice it - no. Is it uncomfortable - no? The fit is 'extra large' which I feel is perfect for my 'medium' size head. I definitely do not have a large head - I would say average - and I wanted a large fit for full coverage. The permits are great because they are big, without being oversized to the point of looking bug eyed. They also wrap around very nicely compared to some other large or x-large styles that extend straight out beyond the curvature of the face. The rubber grips are a really nice feature - they feel very secure on the face - I use a strap occasionally still, but even without they are awesome.
Lens optics are amazing. The silver mirror (which has the copper lens as a base) took some getting used to for me because I was very familiar with more standard dark grey type lenses. After letting the eyes adjust initially - and after using them consistently I can say that they are definitely much more optically pure than my previous poly lenses - super clear. Not too dark, but blocking enough light on bright days too. I really like the lenses.
Looks are subjective - my gf likes them.
Durability-time will tell. Hinges, lens mounting, finish seem durable.