FMA:B is great show to watch. If only because it takes it's plot very seriously. There is practically no filler whatsoever, and every single episode is relevant to understanding the big picture. The cast of characters is large, but they're all characterized well. The antagonists are competent and likable, as well as having a scheme so large and grand that I personally wanted them to win. The internal logic is a little loopy, what with it basically being magic that follows easily bent rules, but it's forgiven for allowing some of the coolest scenes I've seen in a long time to happen. Then, after an absolutely epic and heartwrenching finale, we're treated to one of the happiest and most fulfilling endings to exist in anime.
The only faults I have with it:
The antagonists are competent, but they're not my particular brand of competent, which is a matter where I'm biased. You see, while the enemies were VERY GOOD at what they did, they weren't GOOD ENOUGH. Throughout the last 30 episodes, I got this continual feeling that the enemies were only making short spurts of progress every now and then, while the protagonists were making great leaps and bounds all the time. You see, the antagonists I prefer are HYPER-COMPETENT, so good at what they do that it's insane, and that creates drama by pitting the protagonists against an obstacle that's seemingly insurmountable. Envy, for example, is a giant, huge green monster, who is summarily beaten to death by a little girl, an old man, and a person who doesn't even understand alchemy enough to so much as HARM him. And then again by a single person who he insists on talking with rather than fight. Hell, there was a member of the enemy team that had chronic backstabbing syndrome basically. What I'm trying to say is: sometimes it felt like the only reason the antagonists succeeded at anything at all was because the story demanded it, which I felt was incredibly damaging to my suspension of disbelief.
The only enemy that truly fit my criteria was Wrath, and even he should've been been more difficult, since he had his regenerative-invincibility yoinked away from him at a crucial moment where it would have made more sense for him to have been fully charged and prepared.
Another is that alot of things just plain aren't explained. What's up with the door of truth? Is Amestris and Xing really the only countries to understand Alchemy? What the hell was with the dwarf in the flask?
Lastly, near the end a whole lot of contrived anime cliches start appearing. Edward taking naked, spirit form to combat one of his enemies. The final opponent taking the form of a generic blond-haired muscular Fabio (
Compare'em Toony!), which in itself isn't bad, but it felt especially cliched during his villainous breakdown no more than ten minutes after making his grand appearance.
Then, in the final fight, Eward might as well be channeling the power of Kamina himself with his hotblooded dialogue and fighting style, which isn't necessarily bad, but it was a real jarring change in style and pace. Especially, in the final scene, where Al sacrifices his soul in order to help his brother... but it doesn't really make sense since the final bad guy was basically on his last legs at that moment, and ANY ONE of the many perfectly competent cast, standing no more than 10-15 feet away could have just jumped in and helped Ed, and thus averted the entire problem in the first place, but instead chose to just stand back and watch.