Be a little cautious if you sign up for a profile. For some reason the website allows shoppers to be googled, so if you sign up "Sally Smith" and google your name a few days later you are likely to find "Sally Smith" along with "Mystery Shopper". That may well not be information you would care to share with the world.
I receive emails virtually daily from these guys and they are generally shops being solicited by schedulers that have hit my mailbox numerous times already. I have not yet found it productive, but hope springs eternal so I figure they get another 6 months or so.