His first week, by the numbers:
66.39% of the gross potential for the week was made. 4,203 out of 6,042 seats (6 shows total) were sold. Even if he had gotten all 7 potential shows in, he still would be the Hedwig with the lowest opening week.
For comparison, Neil Patrick Harris made $772,606 (109.57% of the gross potential), Andrew Rannels made $648,738 (82.35% of the gross potential), Michael C. Hall made $600,961 (80.84% of the gross potential), and John Cameron Mitchell made $604,410 (79.79% of the gross potential). Each had 6 or 7 shows their first full weeks.
Another fun fact! Apart from the week of previews (1 performance, $144,194), his first week is the lowest grossing week of the show's entire run. Congrats, Darren!
Sources: 1 & 2, and the nameless (by their request) ONTD member that sent me this! :)
Update: Darren is now retweeting fans for the sole purpose of adding links to buy tickets from.