Dear @dat,
It should be available, make sure to wrap it inside of an event, and remember that you can only use people variable inside - this script is async, so it will only run once the field is ready (other scripts will run before):
fd.spRendered(function() {
var people = [];
fd.field('Persons').ready().then(function(field) {
people = field.value;
//real value is available here, you'll see it in alert:
alert("Inside: " + JSON.stringify(people));
});
//this alert will appear first with message: "Outside: []"
alert("Outside: " + JSON.stringify(people));
});