Picked up one of these myself at Marshalls today, now reduced on clearance to $13. It seems to be fairly breathable and will do as my experimental piece on the whole windshirt idea. On the downside, it fits pretty snug in the chest, perhaps because the brand markets to runners who tend to not be very muscular. Nonetheless, unless you are someone who is an avid weightlifter like myself, I think you may be alright with the size. I am 6' 190lb and I went with a large, where ordinarily I tend to wear mediums. Even with the large, it seems tight in the chest/back and maybe a bit in the arm pits. I suppose the Marmot windshirts would also fit tightly in the chest because they are marketed to runners.
Despite the size issues, it is made nicely with an adjustable hood and waist band. Additionally, you have a hand pocket on either side near the waistband. Unfortunately, neither pocket turns itself into a self contained stuff sack for when you stow the jacket.
Anyway, I'll mess around with this thing when I go out on my next day hike if it is cold enough outside to warrant its use.