I have been a Prime member for almost 8 years now, coinciding roughly with when I stopped having a car. Living in a city without a car has tremendous upsides, but being able to move from shop to shop to find difficult-to-locate items is not one of them. I hardly use Amazon Video, Music, or Fresh and am not in the Amazon Echo or Kindle ecosystem, and still find a tremendous value in being an Amazon Prime member. I'm also not convinced of the value of Fresh due to its small selection compared to brick and mortars + the minimum buy requirement.
If you like the service overall, I highly recommend getting either the Amazon Prime Visa or the Store Card (which is newer, and I haven't had experience with). The card offers 5% back on all Amazon purchases; 2% on all drugstore purchases; and 5% at Whole Foods. In addition, at Whole Foods they will often add 10% off random items for being a Prime member as you check-out. I regularly save ~5% on my overall Whole Foods purchase due to being a Prime member and get another 5% back, so it's roughly 9.75% discount at Whole Foods.
And, seeing as we are on MacRumors, there's a lot of value in getting 5% back on any Apple purchase -- far better than the Apple card, and often at a slightly lower price than Apple Stores as long as its not literally the launch month for a new product. The math is if you expect to spend more than $200/month or $2400/yr (that's one Macbook Pro, easily) on Amazon and Whole Foods, the kickbacks on the card purchases alone will pay for the Prime fee.
If you go this route, you can redeem the 5% back for cash or use it as credits against your purchases in Amazon. Go for the cash back and credit it to your Visa account. It's a better value than using it as a gift card, since you will earn 5% on the purchase if you pay for it directly and earn 0% if you use the Amazon credit option.
If you like a local or national charity, check to see if you can support them via
http://smile.amazon.com which allows you to donate 1% back of most of your purchases to that charity. I always shop via smile.amazon.com, and if you somehow end up at an Amazon.com link, usually the site itself will ask if you mean to shop at smile.amazon.com.
However, Amazon increasingly has lower quality goods listed. It is hard to wade through the junk, moreso than even 4 or 5 years ago. I generally stick to name brands I recognize, try to make sure the item has "Free Returns" listed, and is sold directly from Amazon not a third party seller. Last, but not least, you can call them and tell them not to ship anything via Amazon Logistics. I prefer UPS or USPS as Amazon's own logistics company is just unprofessional - literally your least favorite neighbor driving things around in their minivan. I have had nothing but trouble with it.
Personally, I don't believe it possible to consume ethically under capitalism, so see little difference in using Amazon or Walmart or Target as my "big box" retailer. For things I know my local corner stores *do* carry, I will often get it there so I'm doing what I can to support local retailers which are an endangered species, even if it means spending another dollar or two on the product. So, things like paper products, detergents, light bulbs, etc. I avoid buying online.