3 recent experiences on the three biggies. [Not courier related issues]
Snapdeal: Item was defective. I called up and sent them the snaps. The reverse pickup was done in 3 days and the money was credited in 5.
Amazon: Bought a funky looking razor which was at a 'Deal' price of 279Rs. Item arrived promptly but was shocked to see that the MRP was 199.
Tried the amazon chat and the associate asked me for a pic. I mailed the same and got a confirmation that my refund would be processed immediately (though it was a non returnable item). I was asked to keep the razor

However, even 4 days after the issue I saw the item still bein sold - now at a price of Rs 399. I immediately replied on the previous mail that why the item is being sold. Got a wordy email from a service associate who made no sense. However, the item went out of stock immediately!
Clearly, they don't have a process in place to tie up customer refund requests due to wrong MRP with inventory being shown on the site.
Flipkart: Bought a washing machine with exchange offer. On delivery date, ekart logistics (Flipkart owned) came for delivery with a wrong model numbered machine! I refused to take delivery - my mistake. Should have known that flipkart doesn't take kindly to people who reject wrong products. Anyway, after an hour of deliberation (he with his confused seniors and me reasoning with a mellifluous automated voice on flipkart customer care which assured me that my call was 'important') the guy promised to come back with the correct machine the next day.
In the evening I received a delivery confirmation mail from flipkart. I immediately called up the customer care and the associate bluffed about registering a complaint for the same! Maybe I should have been more receptive to her greetings.
Next day, the flipkart guys came with the correct product but with a wrong invoice (serial number of older product) I immediately called up customer care who simply couldn't understand why I was calling about delivery when I had taken it already. On finally understanding the issue he couldn't give a commitment that a correct invoice will be generated. So, with a heavy heart, I saw my machine being hauled back onto the tata ace. I did get some assurance regarding generating a correct invoice.
I will not narrate the whole ordeal now as its truly frustrating. But, here are the highlights.
1. Overall I had to make 10/11 calls and each call was for an average of 1 hour each. By the 8th call I could accurately guess what they were going to say. By the 10th, I used to finish up the niceties like 'really apologetic'/ 'immediate resolution'/'top priority'/'valued customer'/'24 hours' myself so that we could get started on the real conversation.
2. I got 5 false deadlines from 'managers'/'senior team members'/'relationship managers' about how my machine was going to be delivered in the next 24 hours - which never happened. Wait, i think someone threw in a 12 hour deadline too at one point of time.
3. Twice got these 'commitments' from smooth talking smart-a**es who used a lot of jargon and how just after the call I will get a confirmation from logistics/senior manager/email conf - but it never happened. Yes, I did refresh my browser and diligently checked through spam. Maybe it will come some day.
4. Used up all the channels available to me. A fb page they don't monitor, an email ID which only answers in robotic and few friends in flipkart who sheepishly asked for the order ID and never followed up. Not that I blame them. We customers are really becoming an indisciplined lot.
Finally, after 7 days flipkart took pity on me and delivered the correct product -- with a manually updated invoice number. IFB confirmed that they will honour the warranty which the service associate would fill up on installation and not that phony invoice.
The machine was a birthday gift for wifey thats why maybe I bothered them a bit too much. Flipkart clearly didn't like my choice of gift so I was forced to make other arrangements . Got her a cheesy Archies mug on her birthday when another 'deadline' fell through. Not sure she liked the mug too much
