I bought this a year and a half ago. It works really well. But, when the weather heats up in summer, it runs into problems. It melted onto the dashboard! And became extremely sticky and disgusting. It required a lot of scraping with a paint scraper and a fair dose of white spirits to remove, and there's still a bit of a mark. I even tried waiting until the winter to take it off, in the hope that the cold weather that we're having now would make it easier to remove.
For a point of reference, I'm in glasgow, and we don't get particularly hot summers. This happened during the really hot spell (for us) in late May last year, when it reached 28 degrees. I'm not sure what the in-car temperature was at the time, I'm imagining quite a bit warmer. The car isn't in the shade when it's parked so would have go pretty warm. But 28 degrees isn't exactly tropical, you'd hope that something that's designed to live in what is basically a greenhouse would be able to cope.