http://shoutbox.menthix.net/usercp.php?action=options
Hiding the inserters should make a noticable difference in the loading time of the newthread/reply/edit forms. None of the buttons/menus/javascripts will be loaded.
Just wanted to make sure everyone knew about it...
Edit: Some old related threads...
http://shoutbox.menthix.net/showthread.php?tid=21758
http://shoutbox.menthix.net/showthread.php?tid=24584