I have been an amazon.in customer for pretty long. I have done many purchases on amazon and almost all the transactions have been wonderful.
In 2015, in the month of Oct, there was an offer of 10%/15% cashback offer at amazon.in website on HDFC bank credit cards. I did a purchase of Rs. 5143 on the amazon app and I was informed that the cashback will be credited in my credit card account in the month of Jan 2016. Since then I have been constantly following up with HDFC bank and amazon and none of them is ready to take up the ownership of the issue and resolve it.
So, although I would recommend amazon shopping because of their hassle free return policy but rather go to flipkart as their offers are more reliable.