Hard to say, isn't it? I like the extract, myself, and I use it on my own community, but only on the home page, and I don't use the last reply extract. I think that's more a function of wanting a clean, uncluttered look, though. I could see how it could provide intriguing content, and entice someone into the topic.
Have you seen the Advanced Reporting Health tab? You can get totals there: new posts, new replies, page views, likes. It'd be totals for a period of time, but when you combine that with Leading Content on the Leaders tab, you might get what you're looking for.