These are designed to mount on the roof of an RV, are about the same size as the AC unit they replace, so no worries about profile or wind as some have suggested.
I have not had one, but a friend of mine who camps frequently in the desert swears by them, and has mounted them on his last 3 RVs. I have sat in his RV on a 95 deg day in the desert, and it was nice and cool inside. They work by raising the humidity in exchange for cooling, so they only work in pretty dry conditions. You have to plumb water to them. Would not be of any use in Florida, but in the drier places in California, it can work pretty well.