Evaporative coolers are the best thing since sliced bread in dry climates like southern CA or AZ, but in coastal SC, where in the summer you can swim on dry land with all the humidity, AC is where it's at.
I don't know if they're the *best* thing..... Asthmatics and allergy sufferers tend to have symptoms amplified. I'm both, and growing up using swamp coolers before people realized it amplified asthma and/or allergy symptoms sometimes got rough. Central air, while more expensive, sure was more of a relief.