Prime is waste of money IMO. You can get free shipping on pretty much everything so long as your total order is at least $49 and that is pretty damn easy to do.
The Amazon rewards VISA card is a heck of a deal though. Love that 3% back to use against future purchases.
Like HFCS says, though...prime is not just about the free shipping. We got prime just before we dropped cable. Honestly, for years we did the same, "well, it's not that hard to get to free shipping amount," but finally I realized that to get to the free shipping threshold, I was adding $5-10 to every order of things I arguably didn't need. Sure I used everything I bought, but was I really 'saving' on the free shipping? As well, the free shipping for non-prime is like a week delivery, for prime it's 2 day delivery.
You take the $50 or so that I was spending extra a year to get free shipping and add in the TV shows and music that I listen to, and it's far from a waste of money for our family. For others, maybe it is, but prime is not just free shipping, and it's faster free shipping than non-prime free shipping.