It provides "Consistency of presence data between the presence provider application and Office and improvement of other integration points, including voice mail".
Following are the fixes for presence and IM -
- The presence information that is provided by a presence application is now accurate in all scenarios.
- Instant messaging to distribution lists is no longer supported in Microsoft Outlook.
- The presence icon does not flicker when many people appear at the same time.
- Presence requests from Office applications to presence applications are now handled correctly in all scenarios. For example, a Microsoft Office SharePoint Server 2007 Web page now shows current presence information.
- The icons that are used to display presence data are modified. Users who are red-green colorblind can now determine the status of other users.
- In Outlook Search folders, the count for unread items that are hidden is now accurate.
- When you start an Outlook Search folder from a separate application programmatically, the operation now works as expected.
- You do not have to start Microsoft Office Outlook 2007 to discover a server that is running Microsoft Exchange Server. Outlook 2007 now provides an API to discover Exchange Server servers.
It's a 35 MB download and contains updates to a lot of files including scanpst and update to the API to discover Exchange servers. Find KB936864 here that includes link to the download site.