Okay it's mildly lame to point to John Battelle to talk about Topix.Net but that's the only place I could find Rich Skrenta's summary of new features at Topix. In addition to Gary Price's review, Findory's Greg Linden has a few words to say.
The key nugget seems to be a much more sophisticated NewsRank algorithm. There are also some UI improvements, and I'm just amazed at the number of sources and feeds Topix provides.
Oh yeah, Rich Skrenta, Topix's mastermind, is a Northwestern alumnus. Well before my time though.
Update I probably already knew this, but there is a Topix blog with aforementioned details.