Our nannies have kept their own room, bathroom and the child's room clean and been responsible for their own and children's laundry. They've kept the kitchen and play areas tidy after they've used them, but they've not been expected, nor would be prepared to I imagine, do a full house clean. We've always had a cleaner in once a week.
We've been amazingly lucky and had two nannies who have given our daughter huge amounts of attention and interaction. She has been, and rightly so, the focus of their day, and consequently we have a happy, content and well developed little girl.
I had similar debates to you when we first looked for childcare, but the nanny housekeepers I interviewed did just not make me feel as confident, nor my child as relaxed, as the nannies we hired. I would also say, as someone that is now at home full time without a cleaner or nanny, that fitting in the hours we previously had a cleaner for wth my daughter around is far from straightforward as you don't get 5 hours to focus on it, and consequently I get most done when she is asleep at lunch or before she wakes at 7am. I would not expect an employee to work those hours, or go without a lunch break, so it would bite into your children's awake time quite considerably. However, as I say that's a separate issue to the quality of childcare, and with young children we felt that should be the focus.
I agree with MGMidget, my understanding was that au pairs should not be expected to have sole charge of young children for any great length of time, nor full on cleaning duties, they don't get paid much for those reasons I imagine.