For me, it functions, when i click on a link to a thread that i have read before, it takes me to the first unread post there is. The one time it failed was when somehow auto-login had not worked, and i was directed to page 1, post 1.
Hmm i do not know if i describe this best:
When i go to the Forum list, and select a post thread coloured blue (new posts?) it takes me to the last read post +1, when the line is grey (no new posts?) it takes me to the first post on page one, is this correct?