I bought some Sidi winter boots several years ago and have used them some with good results. Lately I have been riding a bike with
rat trap pedals and
Birkenstock London shoes in temperatures as low as -8F. I have been surprised at how warm the Birkenstocks are, just because of their huge toe box. They also are real stable on the pedals, the tread interfaces well. They are quite inferior to the Sidi boots when I come out of the saddle and hammer, but they're nice for running to the store and back to pick something up quickly.