@W3bbo:Tree view of conversations has been in Outlook for ages. It isn't the default, but it's definitely there.
Outlook 2010 added the new flattened conversation view (which only indents/branches at forks). I like this view a lot since it combines the best of tree view with the tidiness old default view.
However if you like the old conversation tree view, just go to the View tab in the ribbon, click "Conversation Settings" and then click "Use Classic Indented View."
Unless I misunderstood what you want...