I want my tenants to consider me the best landlord they have ever had. I provide quality housing at slightly below market rents, I am very clear with my tenant on what I expect from them, I try to make reasonable accommodations for the various situations my tenants are in, and I respond to maintenance requests quickly.
As for converting this into cash, I think if my tenants regard me as the "best landlord" they will likely stay longer in my properties and potentially refer others to me as well. The savings from reduced turnover and filling vacancies faster is where I will see the financial return.
I agree with the point above about landlords often having a different take on customer service than other businesses. I think it is because the landlord business is a longer term and more involved customer relationship. Also, landlords must always keep in mind to potential losses from a tenant who stops paying and/or damages the property. These concerns are what cause landlords to think too often of tenants as enemies instead of allies in this business.