Personally, I love it because it feels like an unfinished game. Somewhat poorly paced and relatively short, it doesn't take long to platinum, much less beat.
The combat system is fantastic and unique, being pretty much the game's only outstanding component. Meanwhile, the story is simply laughable, and the soundtrack is the same symphonic fare from the other two XIII games.
Most of the hatred it gets is because of the base assessment of "lol, Lightning". I think it's worth playing, as long as you think you'll like it enough.