Note: This bug is raised to the VS tooling/CLR team though I understand that Windows Store issues are owned by the Windows team. Until the Windows team has a connect of its own, I'm filing issues here.
In WPF you can use an ExpandoObject as a view model. In Windows Store apps, you can do the same and the initial values are read into the UI controls, but subsequent changes are not reflected in the UI.
Although ExpandoObject implements INotifyPropertyChanged, the binding system seems to fail somewhere on updates.
My tests show that the ExpandoObject raises the event properly.
A less obvious, cool thing about using ExpandoObject is that it allows code-behind to write to the DataContext using code such as:
((dynamic)this.DataContext).Property = value;
Which compiles and works for both ExpandoObject-based view models and view model classes without having to perform manual type checking and casting.