Actually the 'new' forum is an improvement in that respect. Yes, the first time you log on following the upgrade everything has reverted to unread status, but once you've read the new posts, marked everything as 'read' and logged off, next time only new posts will be highlighted and will not mark themselves as read unless you have actually looked at the thread again since the new post was added - an improvement for those of us who get distracted, as detailed by John in his earlier post (see below):
Originally Posted by John Kennett
Database-based thread and forum read marking
You may have noticed that if you start to catch up on the latest messages but get distracted by the kids, someone at the door, or the boss unexpectedly appearing, by the time you get back to the forums all the messages have been marked as read. No more! Unread messages stay "unread" until you actually read them or mark them as read. You can click on the "Mark Forums Read" link at the bottom of the forum home page, or mark individual sections as read by double-clicking on the status icon
in the list of forums.