Rated 5 out of 5 stars
I had tried nearly every feed reader addon for firefox, and had settled on using the Digest addon. It had it's flaws and was slow, but was reliable.
A friend suggested NewsFox, however, and it completely blows everything else out of the water. The only flaw I've seen so far is improper handling of sub-folders when importing an OPML, but that's it. No other flaws from what I can see so far.