I have been using Mr. Rebates for a good ten years. Oh, I've tried the other companies. When I shop, I open all my rebate accounts to choose the highest percent back. Over all this time, Mr. Rebates offers the highest percentages back.
Don't listen to the commercials. One does not "get paid to shop." One does not "make money" on these sites. However, one can EARN a bonus, like sending in the rebate slip at the supermarket with your store receipt.
To properly write this review, I went back as far as I can. So far, I have earned back over $555. (My ebates.com "big fat check" total for the same time period is about $73 BECAUSE I chose Mr. Rebates, whose percentages are consistently higher.)
For someone whose sporadic purchases are often under $50, I think that's pretty good!