The Strategic Organizing Center and Starbucks Workers United released a new study that says that 90% of Starbucks Corp. ( NASDAQ: SBUX) stores are understaffed and customers face long wait times. Starbucks Workers United and Starbucks management have not always gotten along. BerlinRosen, the PR firm that released the study, has a mixed reputation. The survey is an indictment of new CEO Brian Niccol and his "Back to Starbucks" plan, a set of programs to get faltering same-store sales back on track.