If you're making WPF or WP or even Monotouch and Monodroid applications these days, you're probably familiar with using MVVM to structure your apps. But what happens when you blend the asynchrony and composability of Reactive Extensions with the MVVM pattern? You get ReactiveUI! In this talk I'll introduce the fundamentals of ReactiveUI, dig into the benefits and tradeoffs, and demonstrate some cool tricks that might make your bespoke framework look archaic.