Why'd they hate it? I always hear it as the first thing to be suggested any time someone brings up a power-heavy setting.
I think it was mainly to do with the amount of work that had to go into making all the villains. He's not the type to half-ass anything, so he really put a lot of effort into crafting the storyline and making a lot of villains for us to fight every week. It was his first time running it I believe, so balancing out the fights was probably a big hassle, along with having to create characters with unique subplots.
It was a ton of fun to play though. I'd imagine if one were to utilize more pre-built opponents to fill out the sessions (or possibly create a few missions that aren't so combat heavy to pad out the story), it might be a little easier to run. I do think my GM enjoyed it at least a little, or at the very least he did a really good job keeping things action packed through the whole game. But it's definitely the sort of game that requires a lot of preparation.