Traditionally, the flow of conversion applications tends to be a four step process; enter an input amount, select units of input, select units of output, see computed result. The design of Amount is designed such that the third step is eliminated entirely.
How? The app just doesn’t bother to ask, acts ignorant, and presents every conversion it can. It’s a very well-executed tradeoff. The user-facing cost to showing all conversions at once is very minor, yet the gain is huge. The number of actions the user has to take (when compared to the naive process described above) is slashed by a quarter; anywhere you can reduce user input on mobile device is extremely beneficial. Also, in many circumstances, knowing the other conversions will be helpful — a double bonus.
What’s unfortunate is that the rest of the app is not up to the same standard of brilliance. There are weird, obtuse long-press gestures to delete and copy certain computations. On iOS, the normal expectation is that long presses offer extra context-sensitive options. In Amount, the action of a long press is dependent on where the finger presses on the cells. For apparently no logical reason, long presses on the left and right are converted into delete and copy, respectively. I’m a strong believer in destructive actions requiring two-step processes, particularly when the action to perform is abnormal and uncommon.
I also think the app has suffered from animation overload. The bar button items are animated, which is actually kind of cool, but its mixed in with so much other stuff it slows you down and becomes a chore to navigate between screens. You lose your sense of place as every screen fades to white as it transitions off screen. There is an annoying pulse when you tap on cells. It just feels like too much for an app idiom that I believe should be about straightforwardness and immediacy.
To top it off, I don’t really like the chosen typeface, and the name is stupid: it begs to be pluralised.