The embassy was really crowded, and the security measures are high, so you can't take much with you (including phones).
However the process was organised, and the interview was very quick.
In the end I needed original signatures and some tax forms for the affidavit. So the visa was denied... Or I should say pre-approved. Basically the man at the interview said that whenever I have the forms I need from my in-laws I need to post them with my passport and then they will give me the visa - no need for another trip to the embassy. He also put a sticker on my passport with a code - presumably to speed things up when I send them my passport.