But also very underwritten. All he really needed was one scene to establish his evil BEFORE he met the Jedi. As it is the only person he ever menaced were the two heroes. Admittedly he killed one but that was as a finale, not an establishment of character.
What with all the desert I was often reminded of The Good, The Bad and The Ugly by TPM; if Maul had been a bit more like The Bad it would have been perfect.