As this OS X Tiger update has many things that Apple recommends that are different than previous updates, I thought I would post them to make sure you follow them before upgrading. You can also visit Apple’s help page about this upgrade.
From Apple’s Site:
Important: Please read before installing.
• If you use iSync, you should perform a full sync with your devices before installing this update. Mac OS X 10.4.6 Update includes a later version of iSync with several improvements. For more information and before-you-install steps, see iSync 2.2: Read before updating to Mac OS X 10.4.6 or later, or before first sync
• With the Mac OS X 10.4.6 system software update, PowerPC-based Macs will restart twice, instead of once, after the initial installation.
• You may experience unexpected results if you have third-party system software modifications installed, or if you’ve modified the operating system through other means. (This does not apply to normal application software installation.)
• The installation process should not be interrupted. If a power outage or other interruption occurs during installation, use the standalone installer (see below) from Apple Downloads to update.
• If issues occur during installation–for example, Software Update quits unexpectedly, please see this article.
I hope this helps.