Is RSS working properly?
 

I don't know whether it's my lack of knowledge on RSS, but I'm not sure whether it's working properly.

I was expecting the feed to show me threads that have been changed (e.g., new threads, new posts) since the last update.

However, while I expect a lot of new posts from the feeds that I subscribe to, e.g., from the AA, BA boards, I often see no new updates or only a fraction of the threads that I later see to have changed if I visit the forum normally.

Is there something wrong or am I just doing something wrong?

(I'm using the IE7 reader.)

Yes, it is working properly. It just works differently than the forum, the reason you might not see the same threads is the way they are ordered, threads are ordered by their origination date in the RSS feed, not by the last post to each thread.