Just bought one of these today at Patagonia’s 30% off sale. Previously I was using Patagonia’s Gone Again L/S shirt, but they don’t make that any more.
One of the things Patagonia does well with these shirts is provide the same benefits as a normal trekking shirt (e.g. light, fast dry, bug proof etc) but they make them in nice patterns instead of boring solid colors. Patagonia makes boring trekking shirts too (e.g. Sol Patrol shirt) but the Sun Stretch has quite a few nice patterns.
The Sun Stretch is a bit heavier than I’d like, as the zippered chest pockets add probably an ounce to what otherwise would be a 150g shirt. The zippered pockets will come in handy sometimes, but the Gone Again was probably a better shirt, and it can still be found on eBay occasionally for pretty cheap. I used my Gone Again shirt for the full PCT thru hike and help up well. It only died recently when I put a huge tear in it bushwacking.