They standardized app development on Xamarin to get the benefits of code-sharing while delivering fully native apps. In December 2012, Rdio was able to sim-ship a major update to their Xamarin-based iOS and Android apps.
“Rdio's mobile app is the best looking and best implemented of the three.” (comparing Spotify, Rdio and Google Play)
Because the apps share more than 50,000 lines of code, Rdio was able to release updates for both platforms concurrently and devote more time to new features and user experience.
“Xamarin offers the best of all worlds. We are able to deliver high performance, native apps that, until Xamarin, were only possible with Objective-C and Java. Sharing over 50,000 lines of code across platforms gives us more time to spend on great user experiences.”