Marking this as scaptrap because upgrading jQuery from 1.3.2 to 1.4.2 on WMF wikis may break user scripts and gadgets and the like. The UsabilityInitiative extension is compatible with both.
Also, $wgJQueryOnEveryPage = true; is probably not a very good thing to enable on WMF wikis as long as bug 19586 (jQuery-mwsuggest interaction prevents Opera 8 users from logging in) hasn't been resolved.
$wgJQueryOnEveryPage = true;