Having our nanny has been life-changing. She allows DH and me to have time together as a couple and we're so happy knowing that our children are with a woman who genuinely loves them and is interested in playing with them, spending time with them, and keeping them safe. We travel a lot and have no family nearby and know no other local parents while we're in different cities, so having a trusted caregiver for our children keeps us sane and able to take time for ourselves. I never wanted to hire a nanny or even a sitter, but with DH's long hours I was going a little bit crazy and getting completely burned out, especially after my second was born. Weeks and even months on end with no breaks, no friends or family nearby, no help, and DH gone all the time...never again.
It also gives our kids a bit of a break from us! They adore her and we think it's valuable for them to have access to another adult who isn't us--her special way of playing, her special songs and nursery rhymes, her games, her perspective. We'll be leaving this location soon and I'm just sad that we can't take her with us everywhere.