Rated 2 out of 5 stars
Good for an experimental thing.
It does NOT respect Firefox RSS feeds handler preferences, i.e. it does not register as a feed handler, it just take over rss links without any choice to set back default Firefox feed previewer nor use an external feed reader to subscribe.
That's ok I guess if you intend to replace Firefox's feed viewer in the browser, but as an extension (what it is now) this is IMO just plain wrong.