The only other reason I would require a camper that can handle the extreme cold is that I'm an avid hunter and I go out hunting twice a year on 2 week trips. So it would be nice to have a camper that can house 2-3 people safely and comfortably in the winter time.
I think av8r nailed the two great recommendations for extended winter camping. Although you can stay out in the other campers such as Four Wheel Camper, All Terrain Camper or Palomino, they will require significant insulation and you will burn through propane (unless you get a catalytic heater such as an Olympic Wave 3 or 6). A couple of skiers stayed out in their XP in mountain states with a diesel Webasto heater running non-stop the whole time and were very positive about their comfort.
The other camper brand I'd take a look at is Hallmark RV (
www.hallmarkrv.com). They're made in Colorado so they know cold weather. Hallmark offers pop-up walls with an internal Mylar barrier and insulation. They also offer durable Coosa frames and their exterior wall moulding process ensures minimal seams for cold to penetrate.
Hallmark satisfied all my picky technical interests but their bamboo and stainless steel interior (galley) and roomy dinette were the big convincers for us. I've visited the factory several times...I think they build an outstanding camper and their customer service (see Matt) is top- shelf, IME. I thought we were done shopping. Had my wife not seen the XP, we'd be in a Hallmark Everest.