I too wear hiking boots (one size too large with thick wool socks) when temps get down below 10F. The platform pedals are actually preferred in slick conditions because sometimes I get in loose snow and have to throw a foot on the ground quickly. In temps above 10F or so I have an older pair of Lake MXZ3XX (can't remember exact model) and they work ok but simply are too tight for colder temps.

The key to keeping extremities warm in the winter is to eliminate constriction. Get a BIG pair of insulated boots, put on warm socks, maybe two pairs, and make sure you have lots of toe wiggle room left as well as some room on the sides.