Here's a few things that might news clarification:

1. Leia NEVER met Obi-Wan face-to-face in ANH. When the group landed on the Death Star, Kenobi branched off to turn off the tractor beam and eventually faced off against Vader, therefore he never got to meet Leia.

2. Leia seemed to be a little happy when she heard from Luke that "Ben Kenobi" is with them ("Ben Kenobi? Where is he?"), so her having a little adventure with Kenobi in her early years isn't necessarily retconning ANH.

3. This is just speculation, but I'm gonna build off what Van said. Vader, like Anakin, is extremely prideful. The only 2 opponents we know Anakin decisively lost duels against (except for sand) were Dooku and Kenobi. Now, he got a chance to best Dooku at the Invisible Hand and paid him back for lost half his arm. I think Vader is too prideful to kill Kenobi when he is a shell of his former self. When he saw Kenobi be rescued, he most likely let him go to give him a chance to get back in shape and beat him properly.

4. Once Obi-wan gets his groove back, I do agree with Charles and expect an epic duel. There are 2 factors to a successful Kenobi series, and that's 1. Tell a compelling story about Kenobi Rebuilding his connection to the force. 2. A badass rematch between Vader and Kenobi.