The concept of WhatsApp is really awesome and it is one of the old apps for android platform. I have been using it since 2013 and I am happy with user friendly UI and its features. Google keeps on providing new updates especially video calling feature as an beta edition. There are pretty cool options like sharing documents, audio etc.
But WhatsApp should introduce sticker shop now, which chatterboxes miss a lot. Unlike Hike, Allo - WhatsApp users cannot experience this easy way of communication. The data is very much secured with end to end encryption.
Video calling facility should be improved - and WhatsApp can actually adapt a lot many features from Allo.
Overall, I will give it 4/5.