We have someone come for 4 hours a week. She cleans the kitchen and bathroom top to bottom, dusts, straightens and does floors in the dining room, living room and family room, and cleans two long wooden hallway floors and a large wooden staircase (we have a large Victorian house). She doesn't do the bedrooms or laundry because I feel like I can manage those, or the windows, because there are many and they are large so we just do them twice a year when we are swapping out the storm windows/screens. This way we keep the cleaning costs manageable.
As previous posters have noted, one of the great things about knowing that our cleaning person is coming is that I get on myself and everyone else to put our stuff away and declutter surfaces before she arrives, so she CAN clean when she gets here. We only have her for 4 hours, and I don't want her to waste her time doing the everyday; I want her to do the deep cleaning that I really hate doing.
Also, as I have pointed out to my friends who give me a hard time for using a cleaning person, given my work schedule (50+ hours/week and frequent travel out of town), my family time is really precious. I'd frankly rather hire someone to clean my house so I can spend time with my family, than hire a babysitter or put my kids in front of the TV, or give up precious "couple time" in the evenings, so I can clean house, KWIM?!
I also recognize that I am lucky enough to be able to afford to do this. That said, I would give up a lot (and at times I have) in order to continue to afford it, because having cleaning help so greatly contributes to our quality of life.