I tried to do this one yesterday. Spent an hour at the store and then the app crapped out and wouldn't load anymore. I e-mailed the scheduler saying that I hope I will at least get paid for the time I spent there. No response from her and then she deleted the mission from my assignments. Really disappointing, especially because I've been shopping for a long time!
Pay was supposed to be $55 but I was probably not even a fifth of the way through the items in my list, which means it probably would've taken at least 5 hours in the store to get all of them.
I'm very tech savvy and efficient and I can't imagine how they are going to find people to do these ridiculous shops.