All of the teams that have cleaned our house have been good. The house looks neat and has a very light clean smell. I like being able to call the office and speak to a live person when I need to change my schedule.
Consistency. Merry Maids shows up every time, and the house always looks neat and smells minty when they are done.
Competence. Everything is clean and put away, every time.
Speed. They do it much, much faster than I could myself, but also more thoroughly.