What's the rationale in removing the discussions on the homepage? I found it much easier to dive into discussions before, because several thread titles were displayed, instead of one from each category. Plus, the user's avatar display made it much more interesting visually. Now, you need to click two times before you get to any actual thread (from the homepage). Those little details matter. I know I might get ire for seeming stingy, but I don't know why you'd remove such a convenience for the user.
The Latest Activity felt complimentary to the Discussions, not really a main feature.