Sure - everybody says they have 'happy' customers, and the 'best' service around.
And I'm 6' tall (I'm not).
We know we have happy clients because they tell us. They tell other people, and those people tell us. And then those people tell other people, and those other people tell us.
Plus we have fabulous, amazing customer retention.
What is it, you ask?
Except for a couple mergers and folks that failed to launch: we've lost one client. Ever. Since 2004. Just one.