Configurability is a major issue in the domain of embedded system software. Existing systems specifically lack good techniques to implement configurability of architectural OS concerns, such as the choice of isolation or synchronization policies to use. As such policies have a very cross-cutting character, aspects should provide good means to implement them in a configurable way. While our results show that this is in fact the case, 1) things could have been easier if additional language features were available, and, 2) additional means to influence the back-end code generation turned out to be very important. This paper presents our experiences in using AspectC++ to design and implement interrupt synchronization as a configurable property in the CiAO operating system. Categories and Subject Descriptors D.4.7 [Operating Systems]: Organization and Design--Realtime systems and embedded systems; D.3.3 [Programming Languages]: Language Constructs and Features General Terms Languages, Expe...