I used to think maybe Anakin would have lived a double life for a while, the Vader costume being the disguise. (And traditional Sith armor style to boot.) The big fight we'd waited decades to see should have been while dressed as Vader.

Then, after the whole falling in lava pit thing, the armor also became his life support system, because Vader was already known to many around the galaxy, and the Emperor needed that reputation to continue.

Considering how we only get to Vader proper in the last few minutes of the film, I felt a bit cheated. All those publicity shots of Darth with his lightsaber drawn were damn lies! ;)