An estimation method based on use cases, the use case points method, has given promising results. However, more knowledge is needed about the contexts in which the method can be applied and how it should be adapted to local environments to improve the estimation process. We applied the use case points method to several projects in a Scandinavian software development company as the first activity in a software process improvement project on improving estimation. The second activity of the improvement project was to conduct interviews with project managers and senior developers about how to obtain continued and more widespread use of the method in the company. Based on the interviews, we propose a tailored, potentially improved version of the method and suggest how estimation practices can be improved by applying it. We believe that these experiences may be of interest to other companies that consider applying use case models as part of their estimation practices.