I have a horrible time keeping my feet warm when riding during the winter months. Anything below 40 degrees and my feet get cold quick.
I do also use the dispoable foot warmers, but even those don't do the trick in a good wind.
I've always been on the look out for winter boots that are narrow and with some sort of a slippery heel, so that they'd be safe in a western stirrup. I haven't really found anything.