All lakes here in the Black Hills have at least 4", though most have more now. The larger lakes still have spotty ice on the main bodies, but the bays are good to go. The smaller lakes and ponds have around 6+" now thanks to this cold snap.
Up here in the Grand Rapids, MN area there are lakes with 6+" already and other larger lakes with less. I was out spearing Sunday and there was a good 5-6" of ice. A cop in town told me an ATV went through the ice on Pokegama Lake (large lake) already Monday morning. There are perm shacks out already on some local smaller lakes.