I hired Merry Maids to clean our townhouse after we moved out. They were able to squeeze me in on short notice before the end of the month-- I called Wednesday, had someone come and do an estimate on Friday night, and the cleaning happened on Monday while I was at work. I'm not sure if that's common, but it was great for me.
The cleaning was fantastic - we had lived in the space for three years and never did a deep cleaning, but it sparkled when I checked in Monday night. They were extremely friendly and very clear about what they can clean and what they would charge extra for - the flat fee covered everything but the walls and windows, and I liked not having to worry about a "surprise, it took twice as long as we quoted." They also have a connection to a service master, so we got the carpets steamed as well at the same time.
Overall extremely happy with the service and results.