I have done online purchasing on amazon.in 5-6 times. I have purchased 4 books, 2 mobile phone, 1 antivirus on different occasions. All my orders were fulfilled by amazon. orders were delivered on time(around 4-5 days).
Amazon also offers one day or two days delivery for certain locations, but in that case shipping charges will be high.
Amazon is a market place where lot of sellers sell their products. If any product is marked as "fulfilled by amazon", the quality and timely delivery of the products is assured. In case of any complaint, the product can be returned also within specified time as mentioned in the product listing. Amazon has easy return policy.
I have not faced any issue with amazon so far. Website is excellent and easy to use.