Voip on the go is very efficient way to communicate if you travel a lot. I went on a vacation abroad last week, and I had my Iphone with me. Having Fring and skype accounts, I just whipped out my iphone, find a wifi connection, and voila, instantly connected to friends and family instantly.
It worked really well in most cases, where wifi was available. For instance, most international airports were equiped with free wifi network, so getting on to the network wasn't a problem at all. And without having to be bothered to buy calling cards, I can communicate with my family with a very low cost. Although, I experienced time delay during some calls, but it was very clear and convenient.
Before the trip, I signed up for skype and bought prepaid Skypeout credits. When I tested the connection over personal wifi network at home, I had great results. No time delays nor echos. But, in open public network like airports, libraries, and cafes, delays was pretty much expected.