THE INSTANT VERDICT, SUBJECT TO CHANGE:
The Pros: They have everything. If you can't find it, it doesn't exist. Sometimes the reviews are useful.
The Cons: Literally everything else. Prime costs more and ships slower, the Marketplace is as unregulated as the Wild West, and it's nearly impossible to get customer service to step in on your behalf. The sellers can tell you anything they want, and they don't have to stand by it.
The Verdict: Maybe good for product reviews, but take those with a grain of salt since sellers game the system. For all other purposes, if you can shop elsewhere, do it.
I can remember when Amazon was the premier place on the Internet for customer service. You could get anything and be assured that it would work the way you wanted or you could at least get all or some of your money back.
Consider about 7-8 years ago when I ordered my mother a tablet. The seller touted a one year warranty and the price was right. I got it for her and it started having problems almost right out of the gate.
I contacted the seller, who informed me that it had a one year warranty if I chose to order the one year warranty. Needless to say, this did not please me. I contacted Amazon and explained the situation. They said to send the tablet back and they would refund the money minus a small restocking fee. I felt this was a decent resolution and took advantage. This was the way I expected Amazon to operate so I made purchases without much worry or care that I would be taken care of in the event of something going wrong.
Fast forward to 2020. I ordered an ebike from a seller on Amazon, which was supposedly warrantied for a year. Later, he revised the listing to cover only six months. Regardless, I had a major failure within that six month period. He refused to honor the warranty, instead asking me to perform a series of tests on the bike using a volt meter and a video camera to do all manner of things that ranged from the absurd to the ridiculous (including disassembling parts of the bike myself, or asking me to take it to a bike shop and send him the bill. I couldn't find a bike shop that would work on it).
Did I mention that they offered a $40 discount to write a 5 star review of their product? Yep. I got a card and everything encouraging me to sing their praises in return for some cash. Not only did Amazon know about this (because I told them), they apparently kept doing it long after my purchase.
I petitioned Amazon to intervene, especially when he refused to honor the warranty. I even asked if it was permitted to just say that there was a warranty then refuse to honor it. Of course, their answer was no, but they did nothing but ask the seller to work with me and refused to make the seller take down his ridiculous claim of having a warranty on his products.
Really and truly, Amazon left me on my own. That was a hard one to swallow, as I paid close to $600 for the bike. Eventually, the seller did agree to a partial refund of $250, but that hardly came close to covering my losses.
Recently, I bought a lithium battery for my trolling motor. Again, I went to Amazon. The item got good reviews, so I placed my order, dropping $300 without worrying. The battery manufacturer supposedly warrantied their products for a year, but as I read the negative reviews of the battery, which were admittedly few, the biggest problems came with trolling motor usage. And people who tried to get refunds were tearing their hair out just as I had.
Reminders of the ebike fiasco were starting to rear their ugly heads. People had the same complaints I had with the seller of the ebike...he was not honoring his warranty, he was asking the purchaser to jump through a bunch of hoops, and so on. So, I decided to cancel my order, but I couldn't because it had already shipped. They told me I would have to return it. So, I went to the item page and started to initiate a return. Lo and behold, batteries are unreturnable. Now, anything that USES a battery is just fine, but apparently batteries themselves cannot be returned.
It seems like, when these items are in your cart, instead of upselling a membership to Amazon Prime, they could have a message that popped up, informing you that some items in your cart are unreturnable. But no.
Fine. I'll add the protection plan. Got on a chat with customer service, who informed me that there was no way to add the protection plan after the fact. Fantastic.
Amazon's protection plans are through Allstate/Square Trade. I went to that site and talked to the rep, who said that I indeed could buy one. Go to the battery page, find the offer for the protection plan. Instead of clicking the checkbox, just click the link to open the page for the protection plan. Add it to the cart, checkout, come back to the Allstate site with the order number, and add it there to your plans.
It wasn't hard at all, but I was still mystified why Amazon didn't want to help me. And, in the chat with the Amazon reps, I ended up getting transferred three times before I was finally told no.
It seems that Amazon is now riddled with apathy and incompetence. Almost as if it's a cash cow being milked to support other products or endeavors. I guess failing newspapers and rocketships be expensive, yo.
It really seems like they don't care. That's why I rarely shop on Amazon any more. eBay prices for similar products are often cheaper, and if I pay with PayPal I can get protection for my purchases. In fact, PayPal has been known to go somewhat overboard in siding with buyers in many cases.
Or, I can buy a product on Walmart.com, usually at a price within $5 of what I find on Amazon. In most cases, I can return any product to the store within 30 days and get a full refund. I've done this before, in fact...once I bought a Telecaster guitar kit that wasn't as advertised...went online, chose "Return to Store" and walked right in to my local Walmart with the product and a reference number in-hand. Easy, peasy, lemon squeezy. No questions or hassle.
And they even allow this for batteries.
Why would I take a chance with Amazon when I can do that?
In general here are some good practices to follow to help keep from getting burned online.
1. If the product is warrantied from a known entity with good customer service, like Honda, Panasonic, Minn Kota, Dell, etc., then you can feel safe taking your chances after doing a bit of research. If these manufacturers advertise a warranty, it most likely is legitimate.
2. If the product name is nonsensical or not common English, beware. Koosan, BuyLife, BestWon, VANMUST, TopsRock, Hingkuai, etc. Some of these products might be quite good, but some may also be terrible. You have no way of knowing. Reviews aren't reliable, and even if you know someone who has one, that's a sample of one and is hardly indicative of the whole. Nonetheless, you CAN learn a lot by reading the negative reviews, as they are the ones most likely to be accurate.
3. Watch YouTube reviews. Some are paid promotions, but many are ordinary people who like to share information to help people to make informed decisions. One of the deciding factors, for example, in my recent outboard motor purchase was the video series by the user Gurra detailing his experience with a particular Chinese outboard motor. Look for reviews by people who have a significant number of non-review videos...the people who make a variety of videos are less likely to be sponsored.
4. If the product falls in the "nonsensical or unpronounceable" category and costs over $150, just get the extended protection plan. Especially on marketplace type sites with private sellers, the warranties mean nothing and there will be nobody there to enforce that warranty if the seller decides to ignore you. The protection plan will add only a little more than a tenth of the item cost to the total, so get it and be done with it. Figure it as part of the cost of the product.
In many ways, it seems that customer service has gone backwards as time goes on. But the fact is, most retailers are out to make a buck and individual sellers game the system. You, the customer, will suffer as a result, so it's in your best interest to look out for yourself in any way you can.