I have bought many products at Amazon in the past year and overall I have a good opinion of it. Many of the purchases were Kindle so they do not count for quality and customer service. But the pricing of some of the Kindle editions is fantastic. Some of them are free and on an average they are a 3rd of the price.
Regarding products, I have bought a few and they have been usually good. Some of the products took long to deliver.
Once a wrong product was sent and I sent it back according to the directions given at my cost. The dealer did not respond and Amazon took up the issue and gave me a refund. That is why I find it trustworthy.
Now for the bad part - I had paid a delivery charge and that was not refunded. I had spent money in sending the product back and that was also not reimbursed. So it left a little bad feeling.
I also have a complaint about the cost of delivery. If we buy a low value product many times the cost of delivery is a large part of the cost of the product. There is a lot of complexity in the type of delivery.
The information given on the product is quite exhaustive and better than other sites. Their data is also good and ads are more focussed than other websites though I can see that Snapdeal and Flipkart are catching up.