Actually, the return of the dark fleet is only good when you need forces now, otherwise its a waste of resources in its current state.
Actually, its 10 high level ships(lasuraks, Enforcers, lrf, and the flak frig), without needing to research them, for 60% of the cost normally, and INSTANTLY!
this makes it an excellent source of production once you have more than 2-3 stabilizers. some games, I just set them to autocast and watch the fleet supply counter, researching when I need to. if that's maxed, then 1) my fleet will own any other, and 2) although it'll be carrier heavy, it will have an enourmous destructive potential. and 120 fighter squadrons will own the sky, and will destroy 1-2 capitol ships in one sweep.
This combined with the stabilizer's direct travel make a nearly unstoppable defence, and their phase missiles blow up Advent ships when they still have shields left! And the evacuator kicks ass. I destroyed a fleet when I combined the with a phase disruptor. it was stuck there, not shooting, all the way until I destroyed the last ship. and its nano-disassembler, when combined with volatile nanites and phase missile swarm, will blow up any ship that I decide doesn't need to be there anymore.
And they get resources from destroying your caps. (Salvaging research, 3 civi level)
by the way, I play Vasari.
I am Orodum, and I'm a Night-elf Mohawk. (jk)