Kayo, I agree... that link to view posts since last visit is one of the features I use most. Now you can find it in the row of links on the main forum index:
I think what you're seeking is View new posts
(shows you new posts since your last visit). You can also View unanswered posts
(to give some ignored topics some love), View unread posts
(which shows any threads containing a post you haven't loaded yet), and View active topics
(which show you a list of all new posts from a certain date range, such as posts from the last day, week, month).