Just play the clip, and then come back.
Okay. According to Badass Digest, this is confirmed... yes, Vader says "No!" as he picks the Emperor up. This is yet another change in the Original Trilogy, and yeah, I'm pissed off about it.
It was already such a perfect moment. As Luke, dying under the Emperor's torrent of force lightning, calls out to his father to help him, Vader stares quietly, looks at his son, then at the Emperor, and makes his decision. And he DOESN"T FUCKING SAY A THING. That's what makes it so powerful. You could almost see the thought process behind the mask, as Vader slowly comes out of the fog of 20+ years of evil. It's a grand, amazing moment and the pinnacle of the trilogy, in my opinion.
And George Lucas just ruined it.
Goodnight, STAR WARS. Thanks for the memories.
Update to include another twisting of the knife - Obi-Wan's Krayt Dragon call now sounds like he's getting a hummer in a back alley on Mos Eisley: