I confess I cheated and kept working on it yesterday after the blog post. OTOH, I will not touch it today ;-). Big functionality added, too.
The bad news is that the "next unread article" code and a few others is garbage. It's quite inefficient because I tried to be cheap and not create a coherent model for feeds.
However it works and you will never tell the difference unless you have 2000 articles between where you are and the next unread (in which case the window goes kinda nuts for a couple of seconds).
Still fun!