Fundy is good for serious, prolonged war. But if you are playing your Democracy right, you should be buying the other civs out with all your gold and tech, or doing quick 1-turn wars to avoid the Senate.
Fundy is also useful after you have launched your spaceship - clean up the "problem civs"...
Fundy gives ten free supported military units per city, no corruption, and no Senate interference, but suffers massive city research loss. Research beakers from trade are unaffected. Also you can get away with some poisoning and suitcase nuking that you otherwise would have gotten universally condemned for. The Fanatic unit is cheap and requires no support in Fundy. Good for cannon fodder, but a well-planned war with air, spies, and armor will be much faster.
It has been many many games since I have actually researched Fundy in order to use it.