Better than nothing.
I use this with my North Face backpack which has a shoulder insulation. With the combination of both I haven't had too many problems with freezing, especially once we start climbing for a while and body heat keeps everything pretty warm. There have been occasions where the water in the line froze, 5ºF/-15ºC outside temp range. Solution during those days is just to blow the water back into the bladder. A big disadvantage for me was the lack of a valve, but I just transferred one from my other hose on there.