The pacing is phenomenal; filler is minimal to nonexistent and every episode serves as another step forward. I know a few people who thought that the first few episodes were not explanatory enough, but one of the great things about it is its lack of unnecessarily long narratives; it gives you just enough background information without petulantly walking you through it.
FMAB is also one of the only anime that I prefer the dubbed version over the subbed. The voice actors are fit fantastically in their roles, and the openings and endings were, for the most part, great. The animation was gorgeous as well, especially in action shots.
But I think the most important thing to be taken into account is the plot and characters. At its center, FMAB is about two brothers who have just enough flaws for you to emotionally connect with them, but not so many that it crosses the boundary into overly annoying. The length (64 episodes) allows for steady character development, whether it be for the better or worse. Even the villains have some sort of depth without making it seem like a rushed pity backstory. It can sometimes have crass humor (which serves surprisingly well as comic relief), but it is also harshly realistic; good people die and there isn't always a good reason for it.
So go watch it! I hope you'll love it as much as I do.
