I'm about to embark on a new project in Silverlight 4, and definitely want to take advantage of the MVVM pattern, now I've finally grasped the basics. For implementing commands in Silverlight 4 it seems there are rather a lot of options ranging from the new built-in Command/ICommand option on the Button, over the InvokeCommand defined in the Microsoft.Expressions.Interactivity namespace and on to the range of assisting MVVM frameworks (Prism, MVVMlight etc). Does anyone here have gotcha's, experience and wisdom to share on this subject?