While I find it good that the "unread" marking is much more accurate now, the "New Posts" function got kinda weird. Yes, sometimes it bothered me that some threads vanished after being idle for a while, but now there are like 200 unread threads constantly, and even after marking them read they fill up quickly.
Also I used to be able to click on the "New Posts" shortcut again to simply return to a cached result from a few minutes ago - if I do that now, then the just read posts are really gone from the search results. So if I read or reply to a thread and click on new posts to go "back", then the thread I just watched or replied to is gone, too. Before that they still showed up in the results, but not marked bold as they were already read.