So welcome another addition to Patagonia's massively inconsistent sizing collection. Of course as it's organic cotton, expect it to be one size too big. I'm 5 9', 190 lbs with a pretty broad upper body. Unwashed this shirt fits me loosely. If I lost 5 or more pounds I'd be swimming, so undersizing unless you're a burly dude is the way to go. Fabric is pretty nice, although it drapes a little funny on me. The logo on the back is the money part, but the Diamond C on the front is a little blahzee. I don't really care for front logos either, but its pretty boring. The length...again I'm 5 9' and it comes down to just about my mid quad. Good for the gym, but for a "climbing style" shirt this will be poking out far below your harness. I haven't washed it yet, so I'm torn between seeing if the organic cotton shinks at all, trying a medium or maybe just running 10 miles a day and down sizing.
But if you plan to wear it at the coffee shop with your locking carabiner holding your nalgene to your backpack...this might be the shirt for you.