My wife is just starting to heavily get into mystery shopping and is excited in doing it. She is replacing her previous job at a local video store with this, due to her being unable to stand up for hours (pregnant and all). Not only does she get stuff for it (e.g. free food), she gets paid as well. Another benefit she told me about that I didn't think of was that she sees shopping in a different light. She sees upselling and recognizes it for what it is, instead of what normal people do and pay that $1.20 more for a drink that costs the company $0.02 to produce.
She started out with a pay-for-membership one, but doing some research, she was able to find a few free ones and has a few scheduled now every week for the next 3 weeks. I recommend it for anyone getting out of debt and still wanting to have the "fun of shopping". Just make sure to leave your credit/debit card at home and bring cash only.
Last of all, it's nice to get checks in the mail instead of bills. She just got her first payment in the mail for an hour of rearranging purses at a local shopping mall.