While it's an interesting concept and has some good points, Swipe Calc can cause ample frustration in initial uses. With a few bugs and the lack of upfront tutorial materials to show you how it actually works, the app is hard to figure out in the beginning. If you can get the hang of it, however, you will find a calculator app that performs well, overall.
When you first open Swipe Calc, you'll find a normal calculator. In the current version of the app, the calculator does not work properly in landscape mode, so be sure to hold the machine in portrait mode so that it will take up the full screen. Because there are no function buttons onscreen, it is not immediately apparent what to do. However, if you tap the "i" button in the top left corner, you will be given a quick rundown of the swipes needed to perform each function. It is a simple enough process, but it is hard to remember all of those functions, so you'll be checking back often. Worse is the risk of doing it wrong at some point and accidentally clearing a calculation.
While Swipe Calc works well, the lack of clear direction, no onscreen buttons, and the buggy landscape mode make it harder to use than is strictly necessary. This is a good idea not fully executed so it will be interesting to see the next versions as the developers make improvements.