Hmmm Nikos, I'm going to disagree
There are so many coatings applied to the glass that most of the solar heat is reflected. This is my second summer with the Kuga. I am sure that the interior is cooler inside than with a conventional metal painted roof, which in contrast absorbs heat and because of very little insulation in the headlining, heats the car interior more. I stand to be corrected by side by side testing, but I'm talking to another Kuga owner at work without the glass roof and this is the conclusion.
If you have kids, give them a treat and go for the panoramic view from the back seats. If it's down to just you as a driver, then you won't miss it much as an option, as the view out from it is outside your peripheral vision.