Excellent! That's the definition of
riveting.
First time we've seen Hawaii playing Hawaii, right?
Sun's portentious look back to the hatch where she left Jin...sigh...dead giveaway that Jin doesn't make it.

Probably dies in a valiant effort to stop the ship from blowing up. Michael will most likely die fighting alongside him. That would be an appropriate way to tie up the subplot of their rivalry/friendship.
And
finally we get the payoff with Jack learning about Aaron and Claire! I think Claire has got to be alive on the Island...or
present on the Island...in some form to motivate Jack to go back and rescue her. That might turn out to be his primary motive for going back - but probably not the only one.
So Sun said two people were responsible for her and Jin being on Oceanic 6, her dad and...who?
I kind of assumed Sun was refering to herself when she blamed two people for Jin being on that plane.
That was my assumption, too. It could mean Sun was mistaken in her belief Jin is dead. But if the other guilty party is the person who killed him...
As for Kate's amazingly quick pregnancy...some enterprising reporter could find security footage from the Sydney airport that would show a rather skinny Kate boarding the plane. I don't know who these women are who can hide a pregnancy at six months, but it would be easier if you have some fat on your bones to begin with.
Of course, that assumes a reporter had any reason to doubt her story. The odd position of the alleged crash might be enough.