We looked. We are fulltime in a cyclone using the garage for the bunk room. For now the kids have twin bunk beds. It isn't quite the same as the insulation isn't the same in the garage but it isn't terrible unless you are in extreme weather. If you go that route I would suggest the air conditioner in the main area, and one in the garage area rather than the front bedroom.
We are in a 4100 king. We wanted the rear half bath. With the new exhaust fan installed, it is a great deal. If you can do without the rear 1/2 bath I would go for the 4000 I think. That one has a severest living/kitchen area.
Just my thoughts. If we trade up in a few years and are still full timing we would probably look into a bunk model.
Not that I don't love heartland- we looked at tons of brands with bunk models. The Columbus was one that we liked, as well as an Open Range. But I don't know what their customer service is like. Based on my experience- we would probably try to stick with Heartland as long as they are making a model that we want.