I'd heard the name, but I've never used the app and don't know anybody that does. Though according to this article (http://techcrunch.com/2014/01/20/whatsapp-dld/) they have hundreds of millions of active users, so clearly some people are.
I'm the same as you - heard the name, never used the app. In the recent 4-5 months though all of my friends migrated to WhatsApp. I'm from Eastern Europe and when I cruised around other countries from the region there were many people who used that too. Maybe has to do with the fact that some telecoms still charge insane prices for a piece of SMS when you deplete your free quota.
