How is it possible to feel comfortable with Google's answers when you consider that companies are forbidden from disclosing some information? I'm equally skeptical of the truthfulness of both Google's and the NSA's responses to the revelations.
I'm not able to accept the whole "trust us, everything was circuitously legal so there's nothing to worry about" excuse.
Because you are implicitly claiming that not a single VP, SVP, well known person, etc, would be ethical enough to quit over this if Google had done it wrong. Given who those people are, it seems far fetched.