I live in LA, and I bought this shirt with shadeless, hot hikes in mind. It has 100% delivered. Super breathable! It's also a great layer for all those "should I be wearing sleeves?" moments after the sun sets. It's a teensy bit scratchy at first, but that wears down quickly. I haven't had any durability issues, but I wouldn't walk through brush or do trail work in it either (I wouldn't do that in most polypro-style shirts) An amazing value for the price!
Honestly, I use this shirt in the gym more than on the bike.
Great fit just like the tech T. I was worried about getting a long sleeve just in time for summer but this thing breathes really well and absolutely no stink after a ride.