I'm in San Jose. We don't have it and don't plan to install it. We make a point of opening windows in the morning to let the cool night air in, and keeping curtains closed during the day, etc., to keep the house relatively cool, and that's usually fine. There are two or three weeks, spread out over the summer, when it would be realy nice to have AC, but that doesn't justify the expense, for me.
How hot is it where you are? Do you want to air-condition the whole house all summer long, or would just one or two rooms (say, bedroom and office) work for you?