In Intrepid I was used to enable the autologin feature in gdm, then add the 'gnome-screensaver-command --lock' in Startup Applications to lock the screen immediately after login. This way I was ready to work just inserting my user password. Furthermore, when I started up my notebook with battery and get away from it, brightness was automatically adjusted by gnome-power-manager.
In Jaunty, 'gnome-screensaver' is not immediately started at session startup, instead it's delayed by 30 seconds and there is no way to customize this delay. This makes impossibile to lock the screen.
I've attached a patch that adds a new gconf key ('/apps/gnome_settings_daemon/screensaver/start_screensaver_timeout') and makes possible to customize the delay. It defaults to 30 seconds.
Setting it to 0 causes the 'gnome-screensaver' to be immediately started as it happens in Intrepid, so the problem is fixed.
Thanks for the bug report. This particular bug has already been reported, but feel free to report any other bugs you find.