cocokaylaI agree. Two notifications are helpful - the one that tells you who liked your post, and the one that tells you if someone has mentioned you. If you click on those, you get taken straight to the relevant post. That's great.
The other notification, about people commenting on threads I'm following, is pretty useless. If we've got the time and nothing better to do, maybe we'll make the effort to go hunting through the threads trying to spot which comments we haven't read before. But personally I don't bother, so I'm starting to ignore those while the number of 'unread' posts keeps on steadily increasing.