From Tekrati today:
Directions on Microsoft offers an assessment of the new Windows Update Services (WUS), soon to replace SUS, and to coincide with an upgrade to Microsoft's Windows Update Web service. Currently, this report, a chart comparing WUS and SMS, and related illustrations of the WUS architecture and patch management terminology changes, are available free of charge at the Directions on Microsoft site.
The combination will eventually support updating of all Microsoft products, and it provides some capabilities sorely lacking in SUS, especially status reporting. Although Systems Management Server (SMS) still provides many more capabilities, WUS could appeal to organizations that cannot justify SMSs price tag and greater complexity.