As you know partial page loading is very importamt.
No I do not know this, very important to who for what reason or purpose?
Do you have any plan to doing a makeup UI layer accourding this concept. In my opinion it is nice that we have some specifications for this matter. For example wapping some tag in defaul page by the UpdatePanel control.
No I do not, UpdatePanels are an easy way to do ajax postbacks but should be used very judiciously and only where needed in my opinion.