I did a lot of research before breaking down and buying the official GoPro suction cup mount. The price is unreasonably high but my impression is that it's the best one available. I'll come back and revisit this if it ever causes me problems as, for the price, it better hold up.
I knocked the rating down to 3 for two reasons. FIrstly, it's way too expensive. More importantly though... at this price, they could have included some sort of documentation. There's literally nothing in the box except the hardware. No booklet. No suggestions on how to best use it. Nothing at all.
Maybe this is common sense, but it would be nice if they told you to wet it before using it. I figured that just being clean should be enough to form a seal and didn't want to leave a big mark on my windshield from wetting it. It fell off. Twice. Then a friend said to spit on it first before I put it on and that did the trick. If it was on the outside of my car it would be gone.