The fusion reactor is kind of ridiculous. More risk and less reward? You have to rely on a random chance of getting a fuel cell? Real fusion reactors would be like the Rocket Science ones (very sad to see that mod fall behind) and mad science fusion reactors should give boatloads of power at the risk of turning the surroundings into a rapidly expanding plasma cloud.
It's not that I dislike the idea of making liquid nitrogen and all, but the fusion reactor just seems to be missing a niche in the power section.