The fiance and I order stuff from Amazon regularly. It's a rare week that we don't order at least one thing from them, and often multiple orders, as we order everything from blurays and movies to food and toiletries as we both hate shopping in person.
So it's 100% worth it for us just for the shipping. The streaming is just an added bonus. We don't currently use it much as we just mooch off my mom's Netflix streaming, and I have a Netflix disc subscription with Bluray. I used it before my mom got an account and gave us her log in though, and the selection is decent. Netflix has more, and there's not much on Amazon and not Netflix, but if you don't have Netflix it's not bad. I wouldn't get Prime over Netflix though if you don't need the 2 day shipping.
If you have a Kindle, they also let you borrow one book a month for free if you have Prime. Selection isn't super great though. Some gems in there, but a lot of romance and indie stuff. Unless it's changed it has to be a Kindle and not a tablet/phone with Kindle app to use the lending library.