Those who haven't signed up will have to wait.
Though there are numerous messaging apps like the Whatsapp and Viber, something makes the BBM different. Here it is more confidential and highly secured. The other apps mentioned earlier can be used by adding your friends from your contact list. But with BBM, you will have to send mail to the other person, inviting him/her to join the group. Only if the other party accepts the invitation will you be able to chat.
BlackBerry had planned to launch the BBM for iOS and Android in the last month itself, but it was delayed due to unknown factors. The company is taking every effort to avoid a rush and escape the possible crashing of the company's servers by the first wave of users. The registration method was implemented keeping this in mind.
BlackBerry had earlier announced that about one million Android users were using the unreleased version of the BBM and so were the iOS customers. The current rush proves that people are really excited about the release of the BBM officially for Android and iOS.
Once launched the app, you will be really satisfied to see that the interface of the BBM is just like that of the BlackBerry user interface, which has all the dignity, standard and professional style. Of course it do blend with the current OS too. Both the iOS version and the Android versions are free right now. If you haven't tried it out yet, please go ahead and share your experience here.