I used the chemical warmers last year on a commute to work. At the 7 mile mark my feet were getting cold. I stopped to check things out and found the chemical warmers made my feet SO warm that my feet began to sweat. The chemical warmers got wet and froze! When I took them out they were like ice!!

This year I've been using an old pair of boots (2 sizes too big), poly socks liners, wool or fleece socks, and power-grips on my pedals. So far, so good. I do carry chemical warmers just in case. Circulation also plays a big role in keeping feet warm. Keeping the laces a little loose helps me. I may try the boot covers this year just to see how they work.