Usability is an important factor for search engine acceptance. This paper examines usability of a long query meta search engine. The engine was designed to accept and process an unlimited size query expressed in natural language. We briefly review current search engine usability research and then apply some of the common metrics to various tasks of the search and retrieval process beginning with query formulation and concluding with knowledge discovery in relevant search results. We report on users? utilization of many features offered by the engine which enhance the search experience, increase the quality of the search results and improve the usability measurements. Additionally, the implications of this study on the advancement of search engine development are discussed.