I have been using the agena for a couple months on the AT. It is a great shirt, long sleeves and tail for taller guys and gals. But I do question their customer service. Their socks fell apart after 150 miles and 6 washes. I emailed them weeks ago and have yet to receive a response.
I only used the shirt as a sleeping layer outside of 2 days. So I haven't tested it with much abrasion from my pack. If it is like the socks it won't take much abrasion. Though that's pretty common with merino.
Though for base layer use it fits well and keeps me warm but not hot in mild weather and the same in cold.
Edit: they have since worked with me to get me their second generation sock to replace my first gen pair.
Edit: they have since worked with me to get me their second generation sock to replace my first gen pair.