I've been using the Upside App for about 3yrs now and have accumulated about $2,100 in cash back. Can redeem it for various gift cards (amazon, Applebee's, etc), a prepay visa or to bank account. I have only used the Amazon gift card a couple times and have never linked it to my bank account.
I will say it isn't for everyone as it just depends on where you live and what gas stations choose to participate. For instance in Fargo I can get .25 back at one Circle K but all the others around it are .01-.17. Another thing is if you are doing a points program it doesn't let you double dip so if you redeem an offer on Upside and put then enter a loyalty number at the pump similar to Casey's they will cut your Upside amount down to .04-.08 per gal.