Very fast and efficient. One guy was friendly, the other a little brusque. They didn't seem interested in all the evidence we had compiled showing that my wife intends to re-establish her US domicile (after 20 years in UK). The only glitch was when they informed me that the visa would only be valid for 6 months from the medical date, not the interview date. This is stated somewhere on the consulate web page but we had missed it. Had to do a quick recalculation of whether I could get clear of my UK commitments in time. But no problem. Emerged at 9.15 am very happy!