Just purchased this jacket and it is very light. Unfortunately, a size "large" is too billowy for me, which is strange since I went by the size chart and usually wear large to xl in more athletic or technical jackets. So consider sizing down if you are going to use this in colder applications or for more active athletic use.
I used the jacket skate skiing for 70 minutes in 24F the other evening with a long sleeve medium weight underwear piece next to my skin and the Accelero jacket on top.
Because the jacket is too large on me, the open space it created caused some cold spots. I was exercising at mostly aerobic pace with some minor pushes at anaerobic threshold, and for the most part the jacket was "ok" it wasn't "awesome" as it didn't dry quickly at that temperature and with a little wind, I found it borderline cold for standing around in after the work-out. I don't think it would have been a very pleasing garment at that same activity but for a much longer time.
Post work-out, I just put a warmer jacket over the Accelero and drove home. It dried slightly by the time I was home, it was never soaking wet or anything, but it did seem to retain odor, so instead of just hanging it, I washed it in cold and hung it to dry. It was perfectly dry the next morning.
I went for a run this evening in similar temps in the 20s but with more wind and was very dissatisfied. I have other lighter technical jackets that keep me better insulated and I don't think the jacket's breathability is anything special. In fact, I would say unless you are doing zone 1, or light aerobic activity, this jacket is not a great piece to work out in. I was thinking the weight to warmth ratio would be much better, but it functions very similarly to a straight lightweight nylon jacket warmth wise, but not as good as nylon in wicking perspiration.
I love Arcteryx stuff and would like to try and exchange it for a warmer more technical piece, or in the least for a size medium as a tighter fit might help, but if you are looking for a light, functional and highly technical jacket, this Accelero may not be the one you want.