put baby powder on your toes to keep the sweating down, that helps. changing your socks when you get to your stand helps too but thats kind of a PITA.
If its really cold I use icebreaker bootblankets and a body warmer inside them at the toe, but to be honest theyre a pain to move around in a treestand cause theyre huge. im going to try to find somthing a little more nimble next year.