Great writeup, but just so everybody knows, the cleaning most professionals will do will include the use of an acidic coil cleaner that's sprayed onto the coil fins and foams when it reacts with aluminum and dirt. It will actually push the dirt out from between the fins and gets the coil probably 50% cleaner than just vacuuming and spraying with plain water will do. Also, they should be checking to make sure the pan drains are clear and cleaning the evaporator coils as well.
Luckily for me, my next door neighbor is a 30+ year HVAC/Sheetmetal man. He has all the supplies and services mine every couple years for me. It's amazing what just 1 or 2 years of Sacramento dust will do to reduce the efficiency of the system. I can tell right away, since my programmable thermostat keeps track of usage for the last couple days. For similar days, I have seen as much as a 1 or 2 hours per day decrease in runtime after cleaning.