If you browse the long list of updates for this Outlook 2007 SP2 update (which can be applied to Outlook 2007 SP1 from the looks of it), you'll notice a fairly innocent looking fix:
"When you are running Outlook 2007 and Office Communicator 2007 on a client computer, Communicator unexpectedly creates persistent Outlook connections to Exchange Server."
This is a bit of an understatement because I've noticed a difference in the number of connections (logical and physical) even when Office Communicator isn't involved with Outlook 2007.
To give an example, this is what my connection status dialog box (outlook /rpcdiag) looks like before:
Take into consideration, many times my Internet connection is over an EVDO Rev A data line and the importance of this change skyrockets. I want every little extra bit of bandwidth left for other applications if at all possible.
As pointed out by some of the Exchange gurus at Microsoft, the connections listed in those dialog boxes represent the 'logical' RPC connections back to the Exchange server. The actual amount of physical connections (as in, connections viewable by doing a 'netstat -a -n -o' and filtering for your Exchange client access server) will drop by a smaller amount.
Either way, this has sped up Outlook a considerable amount even compared to unpatched Outlook Service Pack 2, which is leaps and bounds faster than any previous Outlook 2007 version.
This has the potential of reduced bandwidth usage and reduced connection counts on your Exchange server and/or ISA setup. Overall, a great update so far.
Read more about the update and request the binaries here.
Thanks go out to Gary Cooper for pointing out this Outlook update.