Does it REALLY save Money to set Back your Thermostat during the Day?

Seems we have always been told that, if we want to save money, we should set our thermostat up when we aren't home to save money during the summer.  This concept also applies in the winter, but I'm focusing on summer for this discussion.

I was thinking about this.  If I keep the thermostat set, say 76F all day, the air conditioning cycles on and off all day, obviously using energy.  If I set it higher, like 80F while I'm gone, the AC stays off most the day as the house slowly warms up.  Problem is, when I get home, and set the air back to 76F, the AC runs, and runs, and runs; trying to cool the house while it is 100F outside.