No sunburn, but...
We used the sunshade to provide shade for our picnic table while camping in the Sierra at about 5500 ft. The sunshade provides a good amount of shade, but that doesn't mean it is cool underneath. It seems to transmit a great deal of the sun's heat. A shady campsite is preferred.
On the plus side, for its size it is quite compact, easy to put up, and when properly staked it is good in a breeze.