I have only been using her a month, but I am very impressed indeed. Extremely thorough - by way of example obviously she cleaned the kitchen, but discovered a few days later that she had also taken out a grotty pan that I store in the bottom of the oven and given that a clean too.
She was sent to me via Maid2Clean (disadvantage - you have to pay a commision to the agency/advantage - they have full insurance and have fully vetted all the cleaners). It ends up about £11/hr - £7.50 to the cleaner and then £3 or £3.50 to the agency, depending how many hours you have.
I have her once a week, 2hrs cleaning 1 hr ironing.