Amazon Prime really is a good deal. I had signed up for it even before I bought the Fire, just for the free two-day shipping aspect.
After a while, due to its convenience, I found myself buying many smaller items through Amazon Prime that I would have previously bought locally. At one point I had to ask myself whether I really wanted to make all my purchases through Amazon and deny local establishments of my business. In rural and even suburban communities,this may not be a big deal, but I've seen what Home Depot did to local hardware and lumber stores here in NYC (or what Amazon did to mom-and-pop bookstores, for that matter).
Now I try to balance my purchases between local places and Amazon. I'm not asking anyone else to do the same (it's your business where you shop, of course), but I think people need to be aware that the choices they make might sometimes result in unforseen consequences.