It sounds like a good way to stop the cold.Rode with it today at ~35*, fantastic, didn't even wear my insulated boots, feet dry and stayed warm-ish (rode >40 miles) the whole time. I believe that "pocket" of still air it creates is the key, also because it is one-piece, it reduced even more the little bit of turbulence I had at chest/head level. All around a great investment.
Only problem I've experienced was putting them on in the cold...a little challenging to get it stretched tight, but once hooked, done and secure. The velco is industrial and there's lots of it, so there's no flap in the chap at all, even at extended highway speeds.