Ok, have to jump in. This is not directed to anyone or meant to be a flame.
I live on Long Island in NY, the temps this week were 97-100F. I bought a chiller last month, and didn't sweat a thing this whole week, actually I hardly paid attention to the tank temp at all. Before this heat wave hit, I was doing everything to keep temps in the tank from rising higher than 85 with outside temps in the high 70' to mid eighties. I felt the high humidity in this area (north shore) made it very hard to keep temps down. I was constantly calling my wife on hot days, to check on the temp, shutting lights off in the afternoon, throwing ice in the sump and running 6 fans on the tank and sump. Buying a chiller, while not needed during the winter months, I feel was essential during the summer. I too don't understand peoples philosophy of keeping corals with 250-400w MH lighting and not having a chiller. I constantly see posts from people who lose corals and fish to high temps. I don't know about everybody else, but these things are expensive here! If I lost a few nice arcos and other corals, I could be out a few hundred dollars in corals. I whole tank when fully stocked could be thousands of dollars. Chillers are not cheap, and do use a fair amount of electricity, but I constantly see others recommend people taking the plunge to 400w MH systems as, "nothing is too good for my reef" or I'll get better coloration with the higher wattage. I don't really see much of a difference in going to multiple 400w MH bulbs or running a chiller to save your reef, they both suck up your electric bill. People even buy generators that might be used once every few years, but don't have a chiller because they are too expensive. Everything is expensive in this hobby. I bought a ampmaster pump for like $300 when they came out, the $600 for the chiller did not seem that unreasonable and it saves my reef more often then a generator.
I'm not saying that chillers should be thought of as mandatory, but I think people should give more thought to using chillers. They take a huge burden out of reef keeping.