A bit late to this, but I really like Categories and Latest … for a forum that has a reasonable number of users and posts. But I have found that for my brand new forum, the fact that it only shows the last poster of each thread means that it just shows my head on every single thread, as I try to keep people engaged. 
This is unfortunate, because it makes it seem like I’m the only one posting (as opposed to pure Latest, that shows all the faces on every post). But I feel like Latest feels more foreign to people who are used to seeing a list of forums (Categories). So… I dunno. Right now I am keeping it on Latest, so it’s less obvious I’m posting so much, but hope to move the default to Categories and Latest if I can get others to start participating more.