After 12 days of using iOS 7 on my iPhone 5, I can proudly declare that FaceTime Audio is the best new feature in iOS 7. At least it is my favorite one.
I like the Control Center, new Camera app, AirDrop and the overall design of new UI. These additions are great, but FaceTime Audio is awesome. I will tell you why.
Integration, Integration, Integration
VoIP calling is not something new and revolutionary. Apps like Skype, Viber and many others existed for years now, but by adding audio-only calling to FaceTime, Apple made FaceTime the real contender to become the king of VoIP calling. The biggest difference between all existing services and FaceTime is a very close integration of Apple's service into the iOS. It is integrated so well, I don't even notice the difference between making regular calls and using FaceTime Audio. You can make FaceTime Audio calls from Phone app, Contacts app, FaceTime app and iMessage app. If you edit your favorite list in FaceTime app, it will change favorite contacts list in Phone app as well. All apps work in harmony with each other.
Now I use FaceTime Audio everyday, and I don't understand why Apple didn't introduce it alongside video calling when it originally released FaceTime. Maybe there were some troubles with cellular carriers, maybe something else, but after using it for just 12 days, I cannot imagine my iPhone without this great feature.
Great voice quality
FaceTime was a good services before, but sometimes it was difficult to use. For example, I had troubles using it if I had a weak internet connection. I couldn't hear the person I was calling to because it couldn't handle the voice and video at the same time. Making FaceTime video calls uses much more internet data, while quality of audio has to be sacrificed for more smooth experience. With FaceTime Audio, calling is much more stable, because it doesn't require a strong internet connection. It also allows audio quality to be improved dramatically compare to audio quality of FaceTime video calls.
Making a local FaceTime Audio call on iPhone is very simple. To put it simply, there is not so much difference between a regular call and FaceTime audio call. It is great to use. But making an international FaceTime Audio call is a completely different story - it is a pleasure.
Before, when I was making an expensive international call, I had to think about time I spend talking on the phone, but there is no need to do that anymore. FaceTime Audio makes international calls no different to regular local calls.
I travel abroad a lot and I constantly need to communicate with people who live in other countries. Until now I used Skype and traditional international calls, but from now on, I will completely switch to FaceTime for that matter and never look back. I know that I will still need to make regular international calls sometimes, because not everybody have an iOS device, but since the majority of people who I have to be in contact with are already using iPhones and iPads, FaceTime will be enough for the most of the time.
FaceTime Audio is not perfect and it certainly needs improvements, but it is as close to perfect as it gets these days. The following is how I think Apple can make FaceTime even better.
Follow iMessage's example and make FaceTime Audio default way to make calls
For people who understand how iMessage works, the best way to think of FaceTime Audio is as iMessage, but for phone calls. iMessage automatically detects if the recipient of your message uses iPhone and sends iMessage instead of regular SMS. Because iMessage integrated in Messages app, users don't even notice the difference between sending regular SMS messages and sending iMessages.
FaceTime Audio is a little bit different. In order to make a voice call using FaceTime, you have to click on the FaceTime Audio (or video) button. If you don't do that and just click on the phone number, it will make a regular call over the cell network even if the person you call to uses iPhone. If Apple could make FaceTime Audio calls work the same way as iMessage, so it will be able to automatically detect whatever the person you are about to call have an iPhone, and make an FaceTime Audio calls insead, it will completely revolutionise mobile calling experience.
Easier switching between video and audio calling
I hope Apple will make switching between video calls and audio-only calls easier, because now it is limited.
Now you can switch from voice calls to video calls, but it is impossible to do the opposite. I hope that in the future updates Apple will address this limitation.
Support other platforms
If I remember correctly, Steve Jobs himself said that Apple will open FaceTime protocol, so other VoIP clients would be able to make and receive FaceTime calls. It never happened. FaceTime stayed as an iOS and Mac OS X only service.
I understand that Apple wants to encourage new customers to buy iOS devices, but providing basic apps for other platforms may help dramatically increase popularity of FaceTime. They can keep the full-featured apps exclusive to iOS and Mac OS X, but at the same time provide basic apps for Android, Windows and other platforms. I think that customers who want to use full-featured FaceTime will buy iOS devices anyway.
For now, even Mac OS X doesn't supports FaceTime audio-only calls. I expect Apple to add this functionality with release of Mac OS X Mavericks, and maybe in coming months Apple will provide the FaceTime functionality to other platforms as well.