My main use case for CentOS is that I use it as an enterprise server for running multiple software applications like Apache, JBoss, and other middleware software.
I can give you a specific example of how I use CentOS as an enterprise server: multiple software as a service applications are deployed on CentOS servers, running Apache HTTP servers for web traffic, JBoss application server for application servers running Java applications, and multiple other purposes.
CentOS is the closest and best distribution other than Red Hat Enterprise Linux, making it a solid choice if you do not have the budget to spare.