I love insulation that can breathe very well and this definitely does that. My main experience so far has been to put this on as a mid-layer to add extra warmth, it has been below freezing lately. Cold air will definitely go right through this jacket, and that is what I personally want - I can easily take on/off an outer layer to block wind/rain while this gives me something cozy close to my skin that helps keep down sweat.
There is a big downside I've experienced with this jacket so far - the material easily grabs onto other layers and rides up my arms. When wearing alone the sleeves rest halfway down the backside of my hand and the material has some stretch on top of that - which I think is perfect. But after wearing even for a short time it will ride up halfway my forearm until the wrist of the sleeve gets too tight to go any farther. Being cold and having something tight reducing circulation is not a good idea.
I am going to try to add a thumb loop to mine to help hold it down. Otherwise this jacket will drive me crazy unless I am wearing particular other layers that slide better over this material (or wear it more stand-alone). It may also be helpful if they added the thin ripstop material they are using along the outside of the sleeves to reduce the friction somewhat. It would also aid a little with light rain, wind, etc while still remaining very breathable where it counts the most.
The other layers I have used with this so far were other Beyond products. The A5 fleece-lined Rig jacket, and two different long-sleeve baselayers from them as well. I am not sure if the main culprit is it grabbing onto the baselayer, the jacket, or if both are needed.
Perhaps when wearing this with a shell that isn't fleece-lined on the inside it will slide better and this will not happen. I will try that out soon.
Quotes from product description:
"The soft, breathable fabric reduces friction while layering under a shell, enabling greater ease of movement."
"Built for layering - Can be worn as a stand-alone jacket or used as a force multiplier for warmth when combined with a protective outer wind or rain shell. Reduced friction between layers allows for increased range of mobility."