I have a Citi Professional card and just got an e-mail to join Mastercard Easy Savings program. link. It says I'm supposed to get 5% rebate on Avis and stuff like that and 1% on the fuelman network. Does anyone have any experience with this program? Is it really as easy as just using my mastercard and getting a rebate a few days later?

You need a business mastercard. I'm not sure about any other regulations they may have.