Skype is really easy to use. One can connect to anyone in this whole world if one has this application.
The application comes pre loaded on Lumia phones and is one of most downloaded software on Google Play too.
Video calls quality is really nice. If you have a cam you can just get on with it. So no need to spend a lot of money on calls just Skype them!
You will also be able to phone call anyone in this world if you buy Skype credits.
But they Skype has to keep it self upgrading to survive in market.