Palpatine: (after Anakin beheads Dooku) You did good, he was too dangerous to keep alive...
Later, in the Mace/Palpatine duel....Palpatine groveling about being too weak....
Mace: I'm going to end this once and for all
Anakin: You can't, he must stand trial
Mace: He has control of the of the Senate and the courts, he's too dangerous to be kept alive......
Mace seems to be conflicted mentally while Palps is stating he is too weak...and the rest is history. It is nice to see this sort of consistency with this movie as it is carried over into the OT with the Emperor braging about everything going as he has planned it ....including the "disfiguring story" he feeds to the senate to manipulate them, this guy is one big evil. It seems a shame that Lucas wouldn't have had @ least some of the jedi be able to pick up on such a strong evil presence in the force so close to them sooner(making Mace's death more honourable).
I also disagree with some on the voice change of Palpatine being a part of his battle with Mace and the force lightning, being proven in his words to Anakin in the Dooku battle, his true voice seems apparent early on (albeit maybe by accident over the exhiliration of the moment) when he tells Anakin to kill Dooku........all in all, I need at least a second viewing on the big screen just to take in all the elements this movie seems to carry........