Love all the changes you have made so far.
One suggestion would be to add an option in the "Not Read" list to mark all threads as "Read". This was a part of my phpBB forum years back and was very nice. It allows the user to browse the unread threads, read the ones they want, and then clear the list so the next time the user logs in, they don't have to read all the old threads again.
Hope that makes sense,
Thanks!