I never used this before. In my latest game on *tough I declared war on the Drengin and They were more prepared than I had calculated. One of my size 20 planets was deep in their territory from early in the game. I had only 5 "Home Defense" ships with particle beams, and one Destroyer with Harpoon II missiles in orbit.
The Drengin fleet came and wiped out a fleet of 4 of those Destroyers on the way to my planet. When I saw this I rush built the Orbital Fleet Manager (which my spies stole from the Torians

).
When the Drengin fleet attacked the planet, my weak little Home defense ships were dealing out a steady 2-5 damage and my Destroyer much more than normal. In the end, I lost no ships and the Drengin lost six. The same six who had just olbiterated a mucvh stronger fleet!
I normally never rely on planetary defenses aside form one or two "transport deterrents" on each planet. But now I know at the harder levels the OFM can help a weak group of ships become a deadly fleet for the occasional (or not so occasional) defense.
* whichever is above "challenging"