This thing.
Not a bad show by any means, but everything good about the story, it took from the manga, and everything bad, it added itself. Which meant it peaked halfway through the series.
So what’s good? The characters that came straight from the manga all stay strong even when put through events that are unique to the anime and, outside some animation set pieces, that’s the strongest element of the show. Also there’s two tragic events taken straight out the manga that happen in the first half that really hook you into the series.
What hurts it I think are two significant differences to the manga. The first is the change in the way alchemy works, specifically in relation to the homunculi. In the manga, alchemy feels like it’s had the same origins and development as it had in the real world, enhancing FMA’s world as being an alternate version of our history. Changing that really hurt the world building in my eyes. It took it too far from being a pseudo-science and into magic.
The second difference is related to that, but it’s more specific. It’s the character of Wrath in the anime. He is the Scrappy Doo of FMA. He’s supposed to be this tragic, important figure, but he is just annoying. I can barely remember any of the second half of the series as my main memory of watching it is being annoyed at Wrath.
He annoyed me to the point that I’m probably one of the few people who actually thought the movie was an improvement on the ending the TV series had, as Wrath barely played a part in it.
They’re currently airing an adaptation that is truer to the manga, though I’ve not seen more than the first episode as yet, so can’t really compare the two.