When you buy an amazon gift card through Gyft.com, you get 3% rewards points. I lose 1 or 1.5% on the spread (difference between the buy price at coin base including fees and the rate on gift.com; I've tried this on multiple occasions, executing both transactions simultaneously) and I lose 1% cash back that I would otherwise get using my Discover card on Amazon. So the net is that I come out 0.5 to 1% ahead.
Actually you loose 0.0% - 0.5% since buying the Gyft card with a credit card also earns you 1% reward points, according to
Gyft. Fairly negligable difference in that case, granted.