First impression: the UI is really neat, I liked it a lot. Kudos to year team, the execution is excellent!

My understanding is, the app automatically selects one of the currencies based on locality. Would it do the same when I travel?

Obviously missing is entering exact values, e.g. the values that appear on long tap might easily be editable - I intuitively expected them to be while playing with the app.

You might also explain in the guide that for going between the price of a BurgerKing burger and combined GDP of the E.U. you shouldn't scroll all the way to billions but use rounded values instead ;) Similarly for other units.

Also missing: since you have length and volume, area would be nice to have.

Edit: another missing feature is jumping to the beginning of a scale somehow with one tap.