I had blogged about IE8 Downloads and related content when IE RTW (released to web).
IE team blog on MSDN wants you to prepare for automatic download of IE8.
From the source:
Starting on or about the third week of April, users still running IE6 or IE7 on Windows XP, Windows Vista, Windows Server 2003, or Windows Server 2008 will get will get a notification through Automatic Update about IE8. This rollout will start with a narrow audience and expand over time to the entire user base. On Windows XP and Server 2003, the update will be High-Priority. On Windows Vista and Server 2008 it will be Important.
IE8 will not automatically install on machines. Users must opt-in to install IE8. Users will see a Welcome screen that offers choices: Ask later, install now, or don’t install.
If an organization uses Automatic Update to keep Windows up-to-date but wants to manage its own deployment of IE8, a free Blocker Toolkit is available that will block automatic delivery of IE8. This blocker toolkit was released in January 2009 and has no expiration date. For more information, please review the information for IT administrators at the Windows Update/Microsoft Update site on TechNet, as well as the Blocker Toolkit FAQ. Organizations that wish to block the distribution of IE8 should have their blocking in place by the week of April 20th.
Organizations that use Windows Server Update Services (WSUS) and Systems Management Server (SMS) can deploy IE8 in the same manner as they would deploy any other update. We will release IE8 to WSUS in July 2009; it will be classified as an Update Rollup and must be approved to install on groups of clients within the organization.