This feedback measurement is called Net Promotor Score (NPS) and allows you to always have your finger on the plus of your agency.
The benefit of having a system like this in place is it allows you to easily capture nice things people say about you (see Google reviews).
That process, in turn, makes it more attractive for other people, you don't work with, to want to do the same.
That's what I talk to Nick Corrao, John Bachmann and Caleb Stanton, of Social Survey, about all the successful agents they've seen use it.