Whatsapp is hugely popular and nearly all my friends use it daily. It has a better group messaging capability than iMessage but I do use both. Not sure what the Facebook buy out will do to Whatsapp as I've seen some screen shots around the net and it looks worryingly like Facebook messenger with a revised layout. I hope for one they keep it simple and don't over complicate it as it has gained popularity due to it being an SMS equivalent messenger, rather than having a social media influence until now.