In a recent post on how he uses Office 2007 Bill Gates had the following to say about Unified Communications:
A great thing is that all my voice mail, faxes, and even instant messages are sent to my Outlook Inbox using our unified communications technology. Another important feature of unified communications that we have integrated into Office applications is presence and identity. That means I can always tell at a glance whether the person I need to get in touch with is available or not.
For more, see: http://office.microsoft.com/en-us/help/HA102402071033.aspx