Flipkart: Very good shopping experience till now. Bought more than 5 mobiles, 1 AC, etc. (But I have heard they give troubles to replace once delivered, though I replaced one without any issue). Deliveries were slow before, but now surprisingly fast, except during sales where 1 or 2 days get added. (Btw WS Retail has been bifurcated in many new sellers or new ones are created by flipkart's help, they all have flipkart advantage icon. WS Retail is selling very few products now due to govt's notification that no seller can sell more than 25% goods on a marketplace online).
Amazon: Good & use it frequently but had 1 bad experience with a laptop. Seller or someone else had already availed the offer (Free 1TB HDD) on that laptop, it was very tiresome to contact customer service regularly and they did not revert back even once, though after many days they accepted the return. Other than that I have purchased many grocery items, books, 1 other laptop, etc all good. Too much wastage of packing material by amazon. Boxes and boxes.
Snapdeal: Surprisingly unlike others, I have had a very good experience. Bought 1 Laptop, 1 AC, Books, home & grocery items. All were delivered fine and were good. Had no issues. Only once I received a broken tempered glass protector which was picked up the next day itself. The thing is right seller and right products. Selfie with product is a great way to see how the product is and people's take on it. Deliveries are average speed.
Paytm: Another good site, though depends on sellers. Bought 1 HDD, clothing, books, led bulbs & lots of dry fruits. Cashback offers are great. There are some very good sellers in dry fruits who sell best quality, but some send average quality items. But, do check out the products on paytm before you buy elsewhere. DONT BUY LAPTOPS unless it's a PAYTM ASSURED seller, one seller sent me open seal box, thought the warranty was not registered, but it had a manufacturing defect/damage too, so I return showing damaged item received. Return was good and fast. Check seller ratings. Delivery a bit slower, depends on sellers too though.
Ebay: Great for mobile accessories, some dry fruit items (if seller is manufacturer), items below 2000. I shop all accessories from eBay TOP sellers and all experiences have been good. Seller ratings makes it easy to find good sellers. Buy from sellers with 85%+ positive ratings with 200+ ratings OR 90%+ positive with 100+ ratings. I even bought a landline phone which was original with vat bill and warranty. Always enquire with seller if you have doubts. I buy items below 2000 carefree from top sellers (Top rated seller mark is there). Some sellers ship the same day if you order before 5pm.
Jabong: got what was shown. Good discounts sometimes.
Overall my shopping experience has been mostly good except for few returns. Trouble arises for some when they have undue expectations.
Suggestions: in case of electronics and computers always check brand authorized sellers online as most of them allow only some & warranty will be given only if bought from them.