Rated 3 out of 5 stars
The Group feature performs awkwardly. I could only drop-and-drag one feed at a time; I had to continually close and then re-open the Group Options window to move an additional feed. Users should be able to move multiple feeds at on time.
On top of that, the grouped feeds appear not only in the new Group, but they also remain in the parent menu as well. That seems like an exercise in redundancy.
For people with a small handful of feeds, this add-on can be very useful. However, for users with large numbers of feeds that need to be grouped, there are better choices for off-line readers (e.g., RSS Owl among others).