We had The HVAC Service come by to take a look at our air conditioner as it was just blowing air and not cooling the house. They had a technician come in a day or so. Took a look and determined the compressor needed to be replaced but that it would take approximately 3 weeks to get the part in (It was a 20+ year old unit.)
We opted to just get a whole new unit instead of waiting, and they installed it the next day. They arrived when they said they would (they gave a four hour window), installed everything, were courteous, made sure it was working, and they cleaned up after themselves. All around a positive experience.