I also use the archive button and then have a look at the areas that interest me, it's not quite the same as the old unread topics but it gives me the most recent posts and I can easily see which ones I have already looked at. It does take a little getting used to, and I'm sure lots of people are just busy at the moment, so there doesn't seem as many posts as before, but I'm sure in time it will become more like the board we were used to.