Never found him even one bit interesting. As intelligent as a Tyranosaurus, just brawl and no brains.
Even Vader had more charisma than Maul.
I agree that keeping him around would've made the story, as we now know it, difficult.
BUT... with him around for 3 movies, you'd have gotten a different PT, and not neccesarily worse.
The whole issue of the CloneWars could've been dealt differently altogether.
And if Maul had truly been the Vader of the PT, he would've clashed with Anakin in the 3rd part, mirroring the ROTJ-fight, and then the turn of Anakin would've happened in there, not by hacking up Mace.
Or with Dooku.