Some of my users use the "view recent messages" function but I like to believe that most people don't use it because they want to see post in their context. At least that's what I want. =]
But if the recent posts where listed per board it might work better. With a new header for each board and sorted by date within that section. Don't know if it'll look good though, since the list is shown XX posts at a time.
But, staying on topic, the replies-function would be highly appreciated by many of my users. Having to put all interesting topics in the favorite list is not really working since the list becomes very long and is a bit tedious to keep updated.
Maybe all of these different ways to view threads could be collected in a thread viewing function box. Then the user only needs to click the way they want to show posts, maybe they want to see all threads they have made replies to first and click on that function. Then they want to see all new posts since XX and click on that function. After that they might want to show posts from all users that are logged in, or something. Don't know where to put this box though...