Yes, we use ours every time we camp. It was one of the deciding factors in our purchase. The outside refrigerator provides valuable extra space that the inside refrigerator can't. It is mainly for beer, water, pop, and condiments but can fit food for the grill (ours is larger than the little cube style fridges). The outside sink is also very handy when you need to wash up after grilling or anything else. We also have a nice size storage cabinet that we keep all sorts of "outside" things in, and it also has a portable Coleman grill. All of these things keep us from going in and out of the camper whenever we want something to drink or want to prepare a meal.
Could we live without it? Yes. It happens to work very well in our current floor plan (24' couples camper with rear bathroom and dinette slide), but if we were to upgrade to a larger floor plan, maybe a 5er, I could do without. But for now, it works very well for us.