Official Gmail Blog: A small (but helpful) change to 'mark as unread' - http://gmailblog.blogspot.com/2009...
One of my favorite changes. When you read a conversation and mark as unread, it only marks as unread the messages that were unread when you opened it. - Keith Coleman
NICE!!! - Kevin Fox
OMG! I've been waiting for this. I'm very happy. This has been one of my (very few) GMail annoyances. - Cyrus Lendvay