Why would Obi-Wan kill Anakin out of mercy? That doesn't make sense. As the movie states, he was like a brother to him. Obi-Wan would never, ever, willingly kill Anakin. As far as Obi-Wan knew, Anakin would die right then and there in a matter of seconds. It was only by luck/Force that Palpatine found him alive in time.

As for the Vader "NOOOO...", yeah, it wasn't done well. They should rerecord the ADR for that scene. And a minor addition...have Vader break free, and then fall to his knees, unable to control his legs yet, and THEN scream.

Would work better.

But ultimately, if they'd just release the whole Anakin/Obi-Wan fight, I'll be happy.

And Nick Gillard does not suck. He breathed new life into the fighting.