Mr. Rebate: Upromise Alternative

I don't have any children, but I signed up with Upromise years ago, thinking I could transfer the funds to my nieces when they're ready for college. Recently, Upromise announced that you could use your savings to payoff your own student loans, and I was thrilled. Then I found out that my student loan provider isn't a participant. Today, I happened upon Mr. Rebate and this appears to make more financial sense for me. Has anyone else used it, and have you received your rebates?