WhatsApp collected for $ 0.99 as a one time payment for the iPhone app. Now the company has changed their business model that would offer the app free for the first year after that the user would be charged $.99 (~Rs. 55) per year after that, similar to other platforms such as Android and Windows Phone. If you had purchased the app already or downloaded the app when it went free it will remain free for the rest of your life.
WhatsApp has also updated the iPhone app to version 2.10.1 that brings lot of new features including option to send multiple photos at the same time and backup WhatsApp message history to the iCloud. So, when you reinstall the app, you will be prompted to restore from iCloud during the initialization process to get back all the previous messages. They have also released URL schema support for developers that would let them integrate WhatsApp into their iOS apps. You can read more about that in their blog post.
New features in WhatsApp for iPhone v 2.10.1
- multi-send UI: can send multiple photos at the same time
- URL schema support for 3rd party apps
- iCloud chat history backup and restore (WhatsApp > Settings > Chat Settings > Chat Backup)
Download WhatsApp for iPhone from the Apple iTunes store.