A superb first chapter. Very good job introducing the needed elements while still keeping things moving at a decent clip.
Of all of the characters reactions, I think the one that worries me most is Molly's. Harry's in the midst of forgeing his own future and she might try and force Arthur and the rest of the Weasley's to try and make Harry work under Dumbledore.
Also, I liked how you subtly hinted that Albus is not a Light wizard as Harry said he had enough power to open Merlin's vault but that it still wouldn't open for him.