I have performed at least a dozen shops for this MSC when they had the account of one national chain restaurant in my area (chicken wings) which they subsequently lost to another larger MSC (Market Force or MF) who now pays one-third what Satisfaction Services (SS) did. SS's shop report was simple with mostly yes/no and short answer questions, finished by one narrative at the end to describe the entire shop experience, beginning to end. The pay for the shop was $12 but with a generous $16 meal reimbursement allowance. MF scooped that account by cheapening the payout to shoppers (now only $4) but with the same $16 meal reimbursement.
I have done several shops, and never paid the $9.99 fee, just out of principle. I have always been treated fairly by SS, although scheduling is more back-and-forth emails than it is at traditional self-assignment MSCs. It appears to me that this firm is actually a franchise system, so you may deal with more than one franchisee, even on the same job listing site. I have noticed checks from different payers, but again, never had any problems or complaints with Satisfaction Services.
That's my story, and I'm stinking with it!