Service-Oriented Design has driven the development of telecommunication infrastructure and applications, in particular the so-called Intelligent Network (IN) Services, since the early 90s. A service-oriented, feature-based architecture, a corresponding standardization of basic services and applications in real standards, and adequate programming environments enabled flexibilization of services, and dramatically reduced the time to market. Today the current trend toward triple-play services, which blend voice, video, and data on broadband wireline and wireless services builds on this successful experience when reaching for new technological and operational challenges. In this paper, we review our 10 years of experience in service engineering for telecommunication systems from the point of view of Service-Oriented Design then and now.