We bought a 38' toy hauler that had one in it - would have never thought to pay extra for it. Now that I have it, I'll never buy another without one. It does quite a good job at supplementing the furnace when it's really cold in the fall (down to 35 or so at night), and it seems to keep the garage warmer than the ducted furnace does (and the air conditioner heat, which we think is worthless). I carry a small ceramic space heater, but never use it, as I use the fireplace and then keep the furnace just to cover if it gets really cold.
I will also vouch for the ambience on a fall evening after the campfire, or the early mornings before we've rallied to get outside.
Added bonus, Weima-dog LOVES it. :)