sometimes i leave a thread open and come back to reply later. meanwhile new posts could have been published, a sort of notifier is a great enhancement.
Perhaps when you refresh the page, a sort of "divider" showing where the "new" posts begin? And a link at the bottom to go to the oldest-new-post or something.
Live Topic for me actually reduced server loads for me, a lot less refreshing especially on busy days. I'd also like to see this, as an option if nothing else.
phpBB has a good system.
When you submit a post, if any new posts have been made in the meantime, it lists them at the top of the editor and allows you to review your post before submitting.