My GT500 came with the glass roof. I was told or read somewhere that it adds about 20 lbs but actually increases the rigidity of the car. Also, that the tint on is is equivalent to like SPF 50, FWIW.

So far I'm indifferent on it. I live and work outside so I get my fair share of desert sunshine when I'm not driving. I've never actually driven it anywhere the shade open yet. Maybe this winter when it isn't 145 degrees I'll start using it. If I was ordering a new car I doubt I'd pony up the $2k for it. Who knows though, maybe I'll change my mind about it over the winter.