Msexchangeteam.com has published a nice post about Exchange Server 2007 and Windows Mobile 6.0. Some of these new features can be seen in that post.
Shortly after the release of Microsoft Exchange Server 2007, the newest version of Windows Mobile - Windows Mobile 6 was released. Formerly codenamed Crossbow, this release contains a number of enterprise ready features designed to work natively with Exchange Server 2007 to provide a robust mobile experience. In this post I'll provide an overview of the features available when using Exchange 2007 and Windows Mobile 6.0. For comparison, I'll also provide some information about the capabilities of Windows Mobile 5.0.
Read more at source: http://msexchangeteam.com/archive/2007/05/28/439558.aspx