I have one. She's 4. She's great. She's lots of fun and she's feisty.
I didn't know David Cameron had a Nancy when we named her - I doubt he was on my radar much in 2006/2007 - and it might've changed my mind if I'd realised, though I can't imagine her being called anyting else.
I've met about 2 others in 5 years, though I know it's getting more popular.