The old outline format was better because each individual post indicated a "read/not read" color. Now, I'd have to try and remember which posts I've read and which I haven't, because they don't have any indicating color to them. Only the main heading has an indicator color, not the specific posted remarks.
If someone goes away, lets say for a few days and then returns, they'd have to try and figure out where they left off within a topic conversation. The individual messages under a topic were colored green (at least for a few weeks) when read no matter when you logged on to the forum. The new posts were yellow attracting your attention to them for viewing.