Based on mobile computing technologies, ubiquitous systems enable people to access information anywhere and anytime. In addition to the capability of interactivity concerning inquiry processing based on user input through interfaces, ubiquitous systems may offer contextualization and personalization dealing with information filtering based on task contexts and user preferences, which help relieve user effort on the move. This study investigates how different combinations of these major ubiquitous computing capabilities affect user behavior. Using the unifying framework of Activity Theory, it conceptualizes user-system interaction as a tool-mediated activity, the different aspects of which are facilitated by interactivity, personalization and contextualization. It is hypothesized that such capabilities shape user experiences including sense of control, perceived understanding and motive fulfillment, which lead to how ready people are to interact with ubiquitous systems. The results from an experiment support the hypothesized relationships, and suggest that different capabilities interact with each other in their effects. The findings yield insights on how to take a systematic and balanced approach of ubiquitous system design to enhance user experiences.