Plucky is the most promising RSS reader I've ever seen, and what's more, it'll run under OS8/9 as well as X. The app is a $15 shareware package, with free expansion packs that bring the total number of feeds available up to over 4,000, including a bunch I'd never heard of and am now addicted to. Each feed can get its own regex filter, and an iTunes-style searchbox allows for ad-hoc filtering of fetched results. It's multithreaded. It has smart timeouts. I'm in love. Two major downsides:

1. It's not stable. Once I added a couple hundred feeds to my queue, it began to crash every time I checked feeds. I'm going to experiment with the number of threads it opens and reduce the number of feeds in my queue, see if that helps.

2. It's slow, and doesn't make allowances for being slow. Once you've got 4,000+ feeds in your library, opening the feed subscribe/unsubscribe is really slow (understandably). However, one way to make allowances for that would be to allow previews of feeds before they're subscribed to, within the preferences dialog. As it stands, you try a feed out by adding it to your queue, refreshing all your feeds, then, if you don't want it, you have to re-open that prefs dialog (zzzzzzz) and remove it.

A couple other UI niceties, like resizable panes, are missing, but I'm sure they'll come into play soon enough. (Thanks, Hen's Teeth!)