I have a Gore Tool jacket, 40 degrees on down. I use a windshell over it (and some layering) down to 15. Only madmen ride at < 15, especially if there's a wind (we can ski here!).
I have an Airjack, and it is very similar, but a much slimmer fit. The intermediate is really a fine jacket, but not below 40 degrees. At least not for me.