First Day of Week for a Date

         SELECT "start_of_week" = DATEADD(week, DATEDIFF(week, 0, GETDATE()), 0);

This returns 2011-08-22 00:00:00.000, which is a Monday, not a Sunday. Selecting @@datefirst returns 7, which is the code for Sunday, so the server is setup correctly in as far as I know.

I can bypass this easily enough by changing the above code to:
select "start_of_week" = dateadd(week, datediff(week, 0, getdate()), -1);