My biggest issue is that they've all but said Obi Wan is going to face off with Vader, which absolutely breaks the lore of the time between ROTS and ANH...
Does it though? I'm guessing they just use Anakin as flashback material, but I don't think it breaks what we saw in ANH if there is a Kenobi/Vader showdown.
Darth Vader: I've been waiting for you, Obi-Wan. We meet again at last. The circle is now complete. When I left you I was but the learner. Now, I am the master!
Ben Kenobi: Only a master of evil, Darth!
Darth Vader: Your powers are weak, old man.
Ben Kenobi: You cannot win, Darth. If you strike me down, I shall become more powerful than you can possibly imagine.
Darth Vader: You should not have come back.
"When I left you I was but the learner"...Anakin thought he should have been a Master by the time he fights Kenobi on Mustafar. So is he referring to himself as a student of the force or is he talking more about how he was still new to the powers of the dark side, new to the Sith, new to his armor and new body? He could still be a learner in those things when Luke is young. Maybe he loses another duel with Kenobi because he's still a novice, but then feels more like the master when they meet on the death star because he's had another decade of experience as a Sith.
Then there's the "You should not have come back." Come back from where? Come out of hiding? That phrase almost makes me feel like they did meet again at some point between Mustafar and ANH. I don't think another Vader/Kenobi showdown ruins any of this for me - in fact I think it makes ANH seem a bit more realistic in some ways.
I'm hoping we get to see the realization that Vader is Anakin from Kenobi at some point. If Obi-Wan was really all that sheltered on Tatooine, then wouldn't he have been more surprised to find an Armored Vader/Anakin on the Death Star? It's not like he just felt Anakin's presence off planet during his time on Tatooine without Vader picking up on that connection.