I've bought several shirts similar to this one recently and this is by far my favorite. The styling is great, and Arc'teryx never disappoints with the comfort of their items. I bought it for a good slim fit, yet it moves enough to not feel restricting. I couldn't say enough about how comfortable it is.
When I read that this was just over 2 ounces I didn't believe it. But after wearing the shirt it is truly that light. This kept me cool on hot days of almost 100 degrees. It breathes well and is really lightweight.
The Borderline is a very comfortable shirt. It's lightweight and keeps me cool on a warm day. I'm 5'10", 175 lbs, with a 40" chest and the medium was a little snug. Large was a little loose but it seems to have shrunk to fit after one session in the dryer (low heat). I have three of these in different colors and they are great for the office, travel, light hiking, and around town.