Tiger includes a major new graphics technology called Quartz 2D Extreme. Note that this is not the same as Quartz Extreme! Unfortunately, Apple has chosen not to enable this feature by default. It is possible to enable it temporarily via a menu option using the Quartz Debug application included with the Developer Tools. In order to enable it permanently, we have to do a little more work.
One way is to force quit the Quartz Debug application after you have enabled Quartz 2D Extreme from the menu -- quitting normally will disable it again. It is also possible to edit the plist file that controls this feature directly. This file is located in /Library/Preferences, and it's named com.apple.windowserver.plist. Change the Quartz2DExtremeEnabled value to YES. Both of these methods keep Quartz 2D Extreme enabled across reboots.
For more info on Quartz 2D Extreme, see these articles:
Mac OS X Hints
http://hints.macworld.com/article.php?story=2005050121260474