We hired Merry Maids to clean our 1750 sq. ft house biweekly for $100 per visit. They were really great in the beginning. No complaints, but as the months went on, we could tell they started to get lazy. The last nail on the coffin was when we noticed there was still some dirt on the front door mat after one of their cleaning appointments(which we laid inside the house). The mat is the last thing you see when you leave the house. I would think they would've noticed that.
After that, we just cancelled our service. It was worth it, plus I was going on mat leave so we couldn't afford the luxury of a cleaning service. We realized we didn't really miss it afterwards.
It's hard to find a cleaning service that will keep the quality of work up to snuff for the long haul.