Live Replies on Multiply conversations is an awesome feature. Unfortunately, they are disabled in threaded view.
This script tries to address that partially. When new replies are added to the current thread, it shows a notification in the bottom left corner of the page. Clicking on the notification refreshes the page with new replies.
Update: In addition, the script refreshes the viewing history for page owners at the bottom of the page.
Update 2008-05-22: When new replies notification is displayed, keyboard shortcut r or R may be used to refresh the page.
When page is refreshed, new replies are marked so that they are easily spotted. Page now scrolls to first new reply.
Press N to move to the next new reply and P to move to the previous new reply.
Link: 
Very cool...although Reverse is all I need ;) 