I have the Shirt-Jack & it's brilliant! :D
To be fair, it doesn't get extremely cold in the UK, but we do get a lot of sleet in winter & the temperature drops to single figures. However, in those conditions the shirt-jack is perfect. Not warm enough to make you sweat (unless I'm really hiking hard or jogging :rolleyes: ) but perfect for keeping the cold out. Not 100% windproof, but that does seem to improve when it's wet (& when it matters)
My only criticism is that it really needs more pockets. The two breast pockets arent enough & it would really benefeit from some handwarmer pockets.
I'm not sure it would be up to the job of sitting in a treestand for 7 or 8 hours in a freezing wind, but with correct underlayers it's great for stillhunting & stalking.