It's all kind of stupid if you really want to put it to a litmus test. Took me a while to warm up to Maul and his robot horse legs in Clone Wars, but he ends up being a hell of a bad guy.
Well, cause they eventually get rid of the robot horse legs and just give him robot man legs.
But I agree. He's a character that started out stupid as hell. But he shows up like 4 times during the series, and he's a better character each time. To the point where his last appearance is awesome.