I purchased the new Polar therm extremes this year and I am completely satisfied with them. 5 of them fit in a 5 gallon bucket and they do infact keep the hole open to a degree *. On super cold and windy days, lets face it, they freeze up. Not as bad as open hole rigs but they do freeze. They also have a tendency to get burried in snow on real windy days and could be lost in a drift!
Look back a bit for my post on "electrified tip ups" and see what I did with them.
Most important, if your auger is 10" then forget the Therm models because they are only 10.25 inches and have a hard time staying put in big holes.