The Gore Active Shell breathes well. It certainly out-breathes Gore’s current Pro Shell and Paclite (Paclite is Gore’s ultra-lightweight WPB and features a non-textile 3rd layer, similar to a 2.5L fabric).
That being said, I found it quite easy to overwhelm the membrane. On high-output tours where I started to breathe heavy, I almost always had to take the Beta FL off because I was sweating too much. The ~20% increase in breathability (my estimation) of Active Shell over Gore Pro Shell gets this jacket into a breathability realm that, while certainly higher than other Gore fabrics, may be debatable in terms of practicality.
When I am in the mountains, I tend to be either sedentary (gearing up at the trailhead, taking pictures, eating, etc.) or extremely active (skinning, bootpacking, hiking, etc.).
When I am sedentary in the Beta FL, I am comfortable (as I am in most Gore fabrics). And when I am active, I often sweat too much for the breathability of the fabric to keep up (also like most Gore fabrics).
I find the activity zone occupied by the additional breathability of Gore Active Shell covers things like waiting in a lift line in hot weather and skating across cattracks. At these “moderate” activity level pursuits, the added breathability of the Active Shell is most noticeable. But if I’m on a strenuous, 45-minutes boot pack in warm weather, I would likely still take off the Beta FL, as I would a Gore Pro Shell jacket. (And yes, we’re extremely eager to check out the “new” Gore Pro Shell to see how much breathability gain we notice in the real world.)
The Beta FL is deliberately lean on features. It has two main pockets that are large enough to hold one moderately sized climbing skin each (my 175cm, 100mm-wide skins fit, but my 185cm, 120mm wide skins don’t.)
It also features a 3-way adjustable hood and comes with a stuff sack. There are small bits of reflective fabric woven into the shell to aid in night time activities (ie, biking). This is the only jacket in the test without a fleece lined chin. Beyond that, there is not much to report.
The Arc’teryx Beta FL is a jacket designed to keep you dry when you need to be dry. It does a good job of that without the added fluff of many features.