Radlab gives an excellent description of the brown stuff, but unfortunately misses one crucial point: Ski Queen and other Americanized forms of gjeitost aren't actually gjeitost at all: they're brunost, literally "brown cheese" in Norwegian.
Specifically, gjeitost must be 100% goat's milk to qualify. The cheese you find in the specialty cheese section of the supermarket may claim to be the real thing, but I have never come across anything even resembling true gjeitost in the States. Most domestic versions are at least half cow's milk; some are 70 or 80 percent. In Norway, you can buy the real stuff by the kilo, since cheese is basically as much a dietary staple as potatoes. However, it is an... acquired taste, to say the very least. The brunost you find around here is not for the weak of taste bud or stomach, but if you've ever pictured this as the height of Scandanavian depravity, prepare yourself.
The real stuff has a much denser texture. While it will still stick to the roof of your mouth, you need a knife to scrape it off. I transported 2 pounds of it across the Atlantic in a carryon suitcase, and it showed no signs of having melted when I opened the bag 27 hours later. The flavor is pungent like no cheese you have ever had, and most are not foolish enough to eat it by itself; the best results seem to come from strongly-flavored bread or crackers served with it. Aquavit follows nicely, simply because your taste buds have already given up by the time it gets to them. Still, for the true connisseur, gjeitost is a must-have for any koldtbord-type breakfast.