I have a Polish au pair and I am not particularly happy with her. I still feel good about having an au pair, but I think I will ask her to leave when she goes home at Christmas, and replace her with a new one.
She's our first au pair, so I don't know if it's just her, or if it is a Polish thing. She doesn't particularly like cleaning - she does it, but she's not happy; and she doesn't seem to like children very much. She doesn't talk to any of us, so her English is still cack after almost 4 months. She spends as much time in her room as possible, and has made it clear that she doesn't like (or approve) of our food.
But, it is so nice to have someone clean everyday, take children to school, and babysit at night - even if they are miserable. We are used to it now and have a "better the devil you know" attitude.
We are lucky in that DH's employer pays the agency fees as a perk, even if it's multiple times a year. And as I've been told by several other mothers - plenty more where they came from. Ruthless, but true.