In this blog post, András Velvárt details the design decisions and some technical information behind the Windows Phone 7 Mix Zoomery app.
The greatest challenge in porting an application from the web / desktop version of Silverlight to WP7 is that the latter demands a totally different approach to the user experience. You can expect an almost complete rewrite here, but almost none, when it comes to the business logic, client-server communication, models, server side, etc. However, the existing Silverlight development skillset you or your team has is almost 100% percent transferable – the new concepts (such as the Application Bar, the gestures, the sensors, etc.) are easy to grasp. In my opinion Microsoft made the right bet choosing Silverlight as one of the two development platforms for Windows Phone 7, making over 500,000 Silverlight developers WP7 developers overnight.