The arctic kit comes with 2 heaters, one for the engine and one for the interior and battery boxes. It is mainly meant for temps below zero as diesel engines are hard to start when it's really cold. The heater for the engine warmed the engine coolant and oil along with the transmission oil pan. They are really handy in Alaska when you have the truck out in the field and it drops down to 40 to 50 below. Do they do much in the lower 48? Well, that depends on where you live and how cold it gets.
The second heater keeps the batteries warm so they don't lose cranking power from the extreme cold and also heats the interior at the same time. For an M1009 the full arctic heater kit includes a blanket that goes over the top of the back of the truck along with patterns for cutting out wood panels for additional insulation.
But yes, they do have a heater. But that only works once the engine is up and running and has warmed up. But even it doesn't work all that well when the temps are really cold.
I used to own an M1009 in Alaska and would have loved an arctic heater kit.
Ruppster