Feed subscribers have become a very important factor for webmasters to determine their success, and unlike website visitors, feed subscribers get regular updates in their feed readers or through email.
The feed subscribers count changes everyday, and webmasters are always keen to see the number of subscribers and hits to their feeds, to do that they have to either check a chicklet on their site or visit feedburner.com to check on the stats.
Feedburner subscribers is a handy extension that shows you the number of feedburner subscribers, along with the number of hits on your feeds, making it much more easier to track your feed readers.
So if you are a webmaster who frequently checks on the feed readers, this is one extension you should definitely install. You will need to turn on the awareness API in feedburner before you can use the extension.