java builder pattern usage

Recently I saw some of the developers coding their VOs with nested builder class like

public class User {

    private String firstName;
    private String lastName;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public static class UserBuilder {

        private String firstName;
        private String lastName;

        public User build() {
            User user = new User();
            user.firstName = firstName;
            user.lastName = lastName;
            return user;
        }

        public UserBuilder withFirstName(String firstName) {
            this.firstName = firstName;
            return this;
        }

        public UserBuilder withLastName(String lastName) {
            this.firstName = firstName;
            return this;
        }       
    }

}

Now, they claim that this makes code more readable. My point is, this has following disadvantages:

1. I can't simply add fields and expect my IDE to complete code for me, as now I need to update this inner class too.

2. Simple POJOs are carrying code which is not relevant for VO.

I am looking for any advice if I am missing something here. Feel free to add your thoughts about the same.

Sample code after this modification looks like,

User user = User.new UserBuilder()
                .build()
                .withFirstName("Name")
                .withLastName("surName");