Add me to the "Use Them" club.
Two years ago in WY, facing the Black Hills, with a nice antelope buck standing 200 yards below the butte I was peeking over. I set up prone for the shot, just as the sun peaked over said Black Hills. With no sun shade, my Vortex Viper HST would have gone from viewing an antelope buck to a big ball of glowing haze. Fortunately between the sun and the antelope, there was an angle to shade enough of the front lens, that I could make the shot. Without that sun shade, that antelope would have walked.
For the ounce or so of weight, as a practice, if it comes with a sun shade, it goes on the scope. Since my range faces west, I need one anytime I am shooting near the end of the day.
Squeeze