Mini Swamp Cooler (Arctic Air) - Legit?

In general swamp coolers work well in arid climates, but don't work at all in humid climates. I think this is not understood by many people which is you get such varied opinion from people. I also think that the sellers of these type of system should do a better job of pointing out where they will and won't work. If you read most of the advertisements they are always great.