MSExchangeTeam blogged about the architectural changes in the Recover Deleted items in Exchange Server 2010.
Users often delete data from their mailboxes that they later want recovered. Recovery of these deleted items is the most common reason for IT admins to recover data from traditional point-in-time backups today.
With previous versions of Exchange Server, administrators implemented two solutions to enable single item recovery, dumpster and restores. Both had their issues, unfortunately.
Exchange 2010 aims to reduce the complexity and administrative costs associated with single item recovery.
Read more at source: http://msexchangeteam.com/archive/2009/09/25/452632.aspx