Rating: 5 / 5
I highly recommend this hat for sun protection. This hat is light (M=2.5 oz on my scale) and provides full sun coverage due to the long back and wide brim, which allows you to carry much less sunblock and/or one less bandana. It is also ventilated with mesh on the sides of the head. Due to its wide brim and lightness, the chin strap is essential to keep it on your head in wind.
As mentioned in other reviews, the primary downside is the ugly/geek factor. Judge for yourself in the picture to the left of this review (not really that bad, is it?). As a result of the ugly factor, I primarily wear it on backpacking trips, rather than day hikes where I might see people I know (yes, vanity, what can I say . . .). The only other downside is that after repeated washings and folding it to stuff in my pack, the brim is getting a permanent crease in the middle and is a bit flimsy. Despite this, I still give this hat a 5 rating because it is so useful on the trail for sun protection, particularly on the back of the neck and on the side of the head where many other hats that look cooler fall short. When mine gets too flimsy, I'll probably buy another one of the same hat.
Edit: I've changed my avatar so I'm no longer wearing the hat in the picture.