For those of you who may need time to test Windows XP Service Pack 2 in your environment before rolling it out to all your systems, Microsoft provides a tool that allows you to temporarily prevent SP2 from being installed on machines with Automatic Updates enabled (highly recommended, BTW). Microsoft has updated the installation procedure to provide additional time for those needing to test SP2. The duration of the blocking has been extended such that as of 240 days after the August 16th release of SP2, Windows XP SP2 will be delivered to all machines with Automatic Updates enabled.
What this means is that you can enable Automatic Updates for routine patches, without committing to widespread distribution of SP2 prior to testing. You should still try to get your SP2 testing as quickly as possible, in order to take full advantage of the improved security that SP2 offers.