I've only subscribed to threads when replying to a post, then (unlike the old Forum), I only get notification of the first response to that particular thread and nothing after that.
I have, however, been marking entire Forums as read so I can get on what I want (i.e. marking Hammond Forums read because I have no interest in them--no offense intended Hammond lovers!). I wish there were some way to not ever see a Forum unless I wanted to (i.e. Hide This Thread/Forum). I can always go to the Forum index if I want to see something in one of those threads/forums.
Just my 2¢ worth!