I tried at least 10 different currency exchange apps prior to a trip to Vietnam. The Go! currency app was by far the best of them for several reasons. First of all, when large amounts of currency were used, commas appeared on the display making reading them easier. (10,000,000 Vietnamese Dong is much easier to read than 10000000.) Second, I have the paid version of the app and it has the ability to show more than one currency at the same time, which is very useful. (Some tour companies in countries with a volatile local currency prefer to charge in U.S. dollars.) Third, the ability to also factor in a tip or discount by percentages for a total price is brilliant. (This makes tipping in a restaurant or negotiating a discount in a local market even easier.) Moreover, today I was pleased to find that the app was updated and now has a built in calculator which makes jumping from the currency app to the calculator app completely unnecessary. This app has a sleek, intuitive interface that has all the useful functions a traveler needs. I'm very happy with my purchase and have no reservations recommending it to others.