This is great buddy. Earned roughly the same cashback after using this card for over 5 years. Even i used to think there is nothing better than this
Until recently, when i used Axis Magnus (in its prime days), Amex Platinum Travel and HDFC Diners Black to figure out that i can earn rewards of atleast 10% of the amount over and above all amazon discounts (60K cashback now is atleast more than 1.2 lakhs). And i as well buy primarily on Amazon
Give it a thought
Definitely. Using regalia gold right now, creating a profile to get dcb metal and eventually infinia 
If only there was a higher variant of this card with milestones/lounge access. Even at an annual cost I would not have minded that as all my spends are on Amazon and I am sure I am not alone in that.