Affordable software? Right pricing model? Efficient team? Some help from God? Couple of BIG customers? Adopting the right technology? Avoiding age old contracts? Carefully written down SLAs?
May be they are all important; in the sense they help you stay competitive, minimize risks, optimize resources, and cut costs. But what makes your customers keep coming back to you every month after month is TRUST. Remember this isn’t a sell-once-meet-next-year business. This is a trusted partner service. You are not email@example.com anymore. You are firstname.lastname@example.org. The same kind of responsibility you expect from your employee is what your customers expect from you.
Whoever wins that trust, wins the race.