NIKL (a New Implementation of KL-ONE) is one of the members of the KL-ONE family of knowledge representation languages. NIKL has been in use for several years and our experiences have led us to define and implement various extensions to the language, its support environment and the implementation. Our experiences are particular to the use of NIKL. However, the requirements that we have discovered are relevant to any intelligent system that must reason about terminology. This article reports on the extensions that we have found necessary based on experiences in several different testbeds. The motivations for the extensions and future plans are also presented.