While the Android version has been providing the option for sending text messages from the very beginning, iPhone did not offer this ability until Viber 2.0 for iPhone was released.
Strictly speaking, Viber does not send real SMS messages, which means you can send text messages only to other Viber users. Sending a message requires very little amount of data traffic (less than 1 KB), which makes it literally free even on 3G.
If you choose a non-Viber contact, Viber will offer to open the original iPhone Messages application.
With Viber 2.3, you can send not only texts, but stickers, emoticons and locations also. While in the conversation, just tap on massage menu (‘+’ sign). To share a Sticker, slide to the right (left menu), to share an Emoticon, slide to the left (right menu).