Hi Marc Roussel,
Straight onto your questions:
#1. Indeed this behavior with collections which implements INotifyCollectionChanged is a little bit confusing. We'll reconsider it for the next official release (2010.Q1).
#2. You can use EditTriggers property both for RadGridView and GridViewDataColumn with a xaml similar to this:
P.S. Default value of the EditTriggers property means that "F2" key also will put current GridViewCell into edit mode.
the Telerik team