I wouldn't go anywhere near Lake Superior ice until there's a foot or more, and if the lake is heavily iced over. Too easy for a floe to break off.
Some of my co-workers down in Roch will be ice fishing on the Mississippi River swamps over by Winona as soon as they freeze over.
Resorts on Red Lake and Lake of the Woods are showing pictures of 3-4" of ice already, and will be starting their ice ops this weekend.