This paper presents results and experiences coming from 10 years of development and use of XVR, a flexible, general-purpose framework for virtual reality (VR) development. The resulting architecture, that comes under the form of a self-sufficient integrated development environment (IDE) organized around a dedicated scripting language and a virtual machine, is able to accommodate a wide range of applications needs, ranging from simple Web3D applications to motion-based simulators or complex cluster-based immersive visualization systems. Within the framework a common, archetypical structure is used for any application, showing how inhomogeneous needs and technologies can be effectively covered by using a single, rather simple, system organization. We also show how the framework flexibility allows for innovative development techniques such as multiple frameworks coexisting within a single, tightly integrated, VR application.