I have considered implementing some Firefox integration, as it is my browser of choice as well.
So far I am thinking at least a simple plugin that would allow Firefox to communicate with FeedBeast, but if you're asking for a completely integrated feed reader add-on then that is really not the direction I want to take FeedBeast in (you might check out Sage). That said though, there are a lot of things that could be done to make communication between Firefox and FeedBeast easier, perhaps a "Subscribe in FeedBeast" command, and maybe even a way to view articles inside a Firefox side bar.
Browser-side integration is definitely something I would like to do, and may spend some time focusing on this now that 1.5 is released.
Do you have any specific requests for such a Firefox Add-on?
By the way, adding feeds to FeedBeast from Firefox is actually very simple if you set FeedBeast as your preferred feed reader. In fact, you can even set Firefox up such that simply clicking on a feed from Firefox will add it to FeedBeast automatically. To do this, open your Firefox Options dialog and select the Feeds tab and select "Subscribe to the feed using", then click Choose Application and navigate to Program Files\The Little Software Company\FeedBeast™\ and select FeedBeast.exe. Now when you click a feed it will open up in FeedBeast!
I plan to add some tutorial videos to the site when I have some time, and this will be one of the tutorials.
A. Logan Murray
The Little Software Company