There IS in fact general rush for Privacy in addition to their TodayTix lotto, and from what I gather, they've been selling tickets pretty consistently. After learning this, I decided to rush today for the matinee. They released the rush tickets at 1pm for a 2pm curtain (for evening shows, it's 6:00), and I got there at 10:30am. I was 3rd; the first person in line got there at 9am and the 2nd person at 9:30. Nobody showed up behind me until 11:30. At 11:45, a bunch of people started coming. By 12:30, there were probably 20 people there. I didn't stay to find out how many they sold, but I heard from a couple other people that they have usually been selling somewhere around 10 tickets per performance - presumably the unused house-seats.