It would be nice to be able to see how many tasks were in each Context without needing to filter just on each one.
A) You could put the number of tasks into a mouse-over popup text. (i.e. Alt text), so that the number of tasks currently in that Context appears when the user rests the mouse over that Context's "inline filter" text.
B) The most important case is of course where there are zero Contexts. Maybe any Contexts that have zero tasks in them could be greyed out.
PS Maybe the same principles could be applied to the Areas as well.