If you've noticed a 90-second delay added between each package installed by a task sequence (whether from individual "Install Software" steps installing single packages or from a single "Install Software" step processing a variable list) since installing SP1 or certain pre-SP1 hotfixes, you'll be interested in the fix documented at http://support.microsoft.com/kb/955955.  (Be sure to click on the "View and request hotfix downloads" link at the top of the page.  That way you don't have to call Microsoft Support to get the fix.)