I've used PRISM in many of the different applications I have setup over the past 5 years. One of the largest reasons I love using it, is the fact that it works really nicely with IoC containers (We use Unity). We can utilize the two technologies, to setup all the different modules without our application with very minimal effort and code. Additionally, it makes it really simple to implement navigation (Forward, Back, History etc...) and still maintain loose coupling between each of the View/ViewModels.