When Obi-Wan and Vader meet in ANH

Now that ROTS has come and we see how responsible Obi-Wan is for the condition Vader is in, has anyone else noticed the long stare Obi-Wan gives Vader when he sees him on the Death Star? What do you think he's feeling at this moment? Do you think he'd seen holo-photos of what Vader looks like while on Tattooine or is this his first time seeing the half man half machine?

Now that I've seen ROTS I absolutely love this confrontation.

 

Part of your question is kinda discussed here.
For what he's thinking it probably something like "I should have killed him when I had the chance."

 

I don't think Obi-Wan had any idea what Vader looked like after he got his suit. I mean, only VIP's would ever even see the man, so I doubt there would be holo's floating around for the public to see, especially not on Tatooine. Obi-Wan had just imagined what Vader would look like, in my opinion, and looking like that, he wouldn't be hard to find.

 

Obi-Wan probably heard that Vader wore an black suit from travelers (Vader might only speak to VIP's but others can still see him)and used life support. I doubt that Obi-Wan had ever seen the completwe machine.