Set classes in BCL

Mark Seemann has started a vote for the introduction of sets into the BCL. Funny enough I have not thought about them since the Delphi days and got on using generics in .Net and some extra items tacked on the top, but now that Mark has brought it up I can think of dozens of places in code this would have been useful. For more details on this view Mark's post or if somehow I have convinced you you can go and vote directly.