And of course that bit of dialogue between random Death Star soldier and Vader re: Obi-Wan - "Who was he, Lord Vader?" "An man who thought he could help gifted children. He was mistaken" - which is such a great example of Gillan's writerly economy - it indicates a lot about how Vader/Anakin feels about Obi-Wan without spelling it out hamfistedly in detail.

It really is! Between that and his "Obi-Wan never was much of a teacher" to Luke when he realizes Luke has barely any lightsaber training, it's like Vader almost has his hatred for Obi-Wan under control (or it's shot through with some kind of melancholy at his perceived betrayals).

I was intrigued that he didn't tell Palpatine about Luke and his search even before hearing the news from Boba Fett, or, apparantly, of the fact he'd killed Obi-Wan. (At least that's what I take from Vader flashing back to his Obi-Wan duel as well as to Luke when Palpatine asks whether there's been anything else to report, and he replies "nothing".)

I wonder if he held the news of Obi-Wan's death back in order to have something good to report in case things went bad for him again and he needed to get back into Palpatine's good graces (such as they were).