Based on the basic premises of both human-computer interaction research and technology acceptance research, this study investigates the relationship between ubiquitous system design and user adoption. Using the unifying framework of Activity Theory, it conceptualizes user-system interaction as a toolmediated activity. From this perspective, interactivity, personalization and contextualization are the basic design features that enable a ubiquitous system to facilitate such an activity in different ways. It is hypothesized that these system capabilities shape major user experiences including sense of control, perceived understanding and motive fulfilment, which lead to how ready they are to interact with the system. The empirical results obtained from an experiment support the hypothesized relationships, and suggest that the system capabilities interplay with each other in their effects. The finding provides insight on how to balance the capabilities in the design of ubiquitous systems for different tasks and different users.