Viber gives Skpe a run for its money, and we think it comes out ahead. It ships with a good-looking interface dominated by the color purple that will have you placing VoIP calls in no time.

The app integrates with iOS perfectly and, fortunately, doesn't require a username and password to register. Instead, it uses your phone number as your ID. Once you have allowed the app to scan your address book, the contacts registered in the Viber network will appear, and you can start calling them, even if they're based internationally.

We were pleasantly surprised by the audio quality of calls: it was crystal clear every time we used Viber to contact our friends. One of the things we liked best using the app was that Viber is also available for Android, which means you'll see your friends running Android in your contacts list, so you can say goodbye to this type of limitation.

Also, another great feature we appreciated is Viber's ability to allow incoming calls without already having the app open. As soon as you slide to Answer, Viber launches and you only have to wait a couple seconds before you can start speaking.

Overall, we liked how this free app performed during our test. We had no dropped calls or any audio issues, which earns Viber a well-deserved place among our favorite apps.