I recently got these from MEC, and let me say.. they changed my life.

I'm using Shimano MTB shoes, which are basically just mesh, so they let all kinds of cold in.
Previously I had been wearing my thickest wool socks, and then putting plastic sandwich bags over my toes... However, my toes would still start to freeze after half an hour.

With the Booties, I could stay on the bike all day at sub zero temperatures and not even think about whether my toes were cold. They're double layered, so they insulate pretty well, and they keep all the water dripping down my rain pants from going into my shoes.

Now I only feel the cool sole of my shoe from the SPD plate and crank arm heat sink.

I think its warming up enough that I don't need them though.
It was 5°C this morning, and my feet were sweating they were so toasty.