Thats excellent thanks.
Something to indicate when an old post is getting a lot of discussion would also be good (like reddit's 'hot'). As an old post with 100 replies today is listed below a more recent post with very little attention.
The method of guessing URLs works pretty well. I'm not quite sure how http://lesswrong.com/r/all/hot/ works, but it might be what you want.
This link
http://lesswrong.com/r/all/recentposts
gives a page which lists all the recent posts in both the Main and Discussion sections. I've posted it in the comments section before, but I decided to put it in a discussion post because it's a really handy way of accessing the site. I found it by guessing the URL.