Successful implementation of a first-/last-mile automated bus (AB) service depends on consumers' actual adoption of the service. Consumers, when decided to take an AB ride for the first time, shall rely on their expectation of the service and capabilities of the technology. After the first ride of the vehicle, their value assessments of the service are further refined based on their actual ride experiences. Whether the operators can retain the users highly depend on such assessment. Thus, it is immensely important, when investigating users' adoption behaviour of a first-/last-mile AB service, we take into account the longitudinal changes of the users' valuation of the service. This is the research gap that this study is contributing. During a first-/last-mile AB service trial in Stockholm, Sweden, a panel data involving 185 respondents was available for analysis. The first survey was shortly after the launch of the trialled AB service and the second one was four months later. Structural Equation Modelling was used to investigate the changes of users' judging criteria across different socio-demographic groups, due to initial usage and the subsequent usage. The results show that the concerns affecting the users to continue with the service change with an increase in the ride experience. Willingness-to-use of the experienced users was initially affected by their level of appreciation with the safety and travel time with the service. However, ride comfort became a dominant factor with increasing ride experiences.