While extending SharePoint 2010 Ribbon with new functionality one of the common things you do is to check whether a command should be enabled or not. Since the checking function expects you to return a value it can get tricky if your custom checking operation is asynchronous. Find out how to asynchronously check if a Ribbon command is available.
SharePoint 2010 ships with a new User Interface framework that allows you to easily create rich user experiences. While developing custom solutions one of the challenges is to communicate long-running operations with the user: after all there is nothing more annoying than a non-responsive UI. Find out how the new UI framework of SharePoint 2010 supports communicating the progress notifications to users.
SharePoint 2010 ships with the new Modal Dialog framework that allows you to display dialog windows in an unobtrusive and user friendly way. This is extremely important when creating user friendly solutions as it allows users to preserve their context while providing some additional information. While the new modal dialog framework is definitely a great idea, there is one thing missing in the implementation: support for communicating with custom application pages.