FYI: I found an interesting article from TechNet magazine, that describes some of the OC GUI enhancements of Exchange 2007 SP1:
Improvements to Unified Messaging
Unified Messaging was an exciting part of the initial Exchange Server 2007 release. Service Pack 1 builds upon this functionality, introducing many new features and enhancements. Some of the features require you to deploy Office Communications Server 2007 in the same Active Directory forest, but there are many features that don’t require Office Communications Server. I can’t cover all of the changes to Unified Messaging here, but I will run through some of the notable additions. If you want to read more about Unified Messaging, check out “Deploying Unified Messaging with Exchange Server 2007″ in this issue of TechNet Magazine for more information.
First I’ll touch on some of the new features that do require Office Communications Server 2007. There is now support for media streams to traverse firewalls and for high-fidelity voice messages. There is notification of forwarding when leaving voice messages when the destination uses call forwarding. Users can access Outlook Voice Access from Office Communicator 2007 without entering a PIN. There is integration of missed call notification e-mail messages and voicemail notification with Office Communicator 2007 (see Figure 5). And much more.
Figure 5 Voicemail notification in Office Communicator
One of the enhancements to Unified Messaging that doesn’t require Office Communications Server is support for the Secure Realtime Transport Protocol (SRTP). The initial release of Exchange Server 2007 offers two security modes: unsecured and secured. The secured mode only encrypts the Session Initiation Protocol (SIP) traffic, and the RTP traffic is unencrypted. In SP1, there are three modes: Unsecured, SIP secured, and Secured. In SIP secured mode, only the SIP traffic is encrypted, not the RTP traffic. In Secured mode, both the SIP and RTP traffic are encrypted. You can also configure Mutual Transport Layer Security (MTLS) for dial plans using the Exchange Management Console.
Other changes include the new Enable Unified Messaging Wizard, which you can use to add an SIP or E.164 address for a user; configuring the URI type for a dial plan using the Exchange Management Console; and Quality of Service (QoS) support using DiffServ for tagging media traffic was added to SP1.
Full article here: http://www.microsoft.com/technet/technetmag/issues/2007/12/SP1/default.aspx