This study examined the implementation of an open source library automation system, Evergreen, in Indiana public libraries and its impact to library users. Three-hundred-forty-nine participants recruited from nine public libraries completed a quarterly user survey regarding their history at the local public libraries and their use of the previous OPACs and the Evergreen OPAC. The implementation of the Indiana Evergreen System received a moderately positive mark from the participants and the positive mark was related to the use of the ILL library function. The ILL service satisfied the participants’ needs; in the meantime, the service also motivated them to use the Evergreen system. Initial benefits for the Evergreen users are confirmed in this project. As open source ILS aim to enhance library services through better library management systems, we also believe improved ILS will be based on increased understanding of users.