I use Viber out and just add $5 credit every few months. I dial international numbers, mostly banks and stuff in Australia where I might be on hold for 15-30 minutes.
It is very handy as it allows me to use it for 13 numbers I just add the +61 and the 13 number (phone banking etc) and it works well. If Viber is registered to your number from back home it will show up as you calling, my Aussie mobile number shows up at their end.
Service is good, rates are great. I recommend it at least for $5 trial credit. If your internet is good here at home then the calls are often better than direct dialing.