Over the past five years, the MyCampus group at Carnegie Mellon University has been developing and experimenting with Ambient Intelligence technologies aimed at enhancing everyday life. The project has drawn on multiple areas of expertise, combining the development of an open Semantic Web infrastructure for context-aware service provisioning with an emphasis on issues of privacy and usability. In this paper, we review key motivations behind the project, discuss the MyCampus Semantic Web infrastructure and report on our experience tailoring the architecture for different environments (e.g. everyday campus life applications, office applications, museum tour guide). This includes a discussion of Semantic e-Wallets aimed at reconciling user demands for context awareness and privacy as well as a description of different context-aware applications developed and evaluated during the course of the project. We also discuss our experience using Case-Based Reasoning (CBR) functionality developed to overcome usability issues associated with capturing complex, context-sensitive user preferences. The paper concludes with a summary of lessons learned so far and of challenges still to be addressed.