I use it for free calling when traveling, you can call other telerific users free and Family is also free. Voice quality on Wifi is far better than skype, Whatsapp and google
+1
Quality is very good, and the UI is neat. Great app.
The main reason I signed up was, that they also provide a phone number (like GV) and they have 718 numbers, most are good ones too. The only downside is that in order to receive calls the app needs to be running in the background, otherwise it goes to voicemail.
ETA: IDK if it's still available, but when I signed up I got a $15 balance for $10.