Its been around 5 years when I first started using whatsapp messanger. Its very userfriendly and best way to communicate with my friends. It contains features like I can send pictures, videos, audio files, double blue right mark for receiving and reading messages, calling feature is also there and soon video calling feature will also be there. Its free to download in any operating system and now its lifetime free means now I can use whatsapp without any subscription.
But you can only talk to those who are there in your contacts and using whatsapp. The only thing which I dont like is that there is no scope for making new friends but still its very user friendly.