I only ever use Flipkart to order office supplies etc and have used them to purchase a mobile phone in the past also. I have used them on 8 or 9 occasions and I have only ever had good experiences with them - its sad to read the bad reviews however but I’ll bet if everyone who received a good service from Flipkart actually wrote about such good service it would far outweigh the negative experiences.
Sometimes you just have to put things into context. I would personally recommend Flipkart :)