I'm ignoring the above post because it looks boring.
The Vader costume is also going to look different from the Vader we see in the OT.
Another thing that I'm surpised that I did not mention let alone of you guys is that there is a Jedi Traitor amongst the ranks of the... Jedi. He/She is the dude/dudette that erased the Kamino files in the Jedi Archives and it is rumoured that he/she'll be killed by Mace or Yoda.
Like in ROTJ when Palpatine tries to lure Luke to the darkside by telling him to strike down his father there is supposed to be a scene that parallels this in Ep3. Apparently Palpatibe will tell Anakin to release his anger, let out his hate and strike down Tyranus where he stands.
p.s. Lucas has said that REVENGE OF THE SITH is not a title he'll use and that pisses me off, what title would be better?