I thought it was great!
Probably I'm overrating it a bit since Sark was in it, but never mind..
I thought it felt a bit like "the good old days", but with Rachel in the field instead of Sydney. There was action, tension, romance, family (and Sark) in a way that Alias used to be.
I loved Jack and his MI6 friend. Wonder what their history is? But don't you think SHE is the double agent inside MI&? That would be typical, since Jack likes and trusts her, and he's our tragic hero so he all his friends are bound to betray him...
And I really really really loved how Sark played all of them, especially Rachel, when he refused payment for what he did. Now they are in his debt... Cleverly played.