It's not the highest ROI play, but it's free money, yes. Just keep in mind, if you want to play that strategy it doesn't make sense to deposit, bet that market, and then cash out. It's better to bet that market, and then cycle that money through other free money markets later on before cashing out. This is because you have to pay a 5% withdrawal fee. Also, make sure you deposit with a CC that gives you the highest cash back percentage. I'm getting 2.25% on my deposits.