Have tried a number of free and cheap calculators, but in the end I chose this one over all others, in spite of it being a ridiculously expensive app, considering it essentially performs pretty basic tasks.
So, what are its great features?
First, it has a clear and basic looking interface that seamlessly matches the way iOS 7 and 8 look. No fancy keys shining in too many colors, nor 3D effects or the like. Focus on the essential only.
Second, when in landscape it has a tape at the left side, which is exactly where it should be if you're right-handed - sorry lefties. (Plus: that tape can be emailed out.) Better still, it has a simplified 'current' tape (=clears everytime you hit '=', which you ONLY need to do at the END of a calculation), which runs along right below the main digits, even when in portrait mode. Nice!
Third, the A/AC button, backspace and '=' are at the leftmost column, instead of the first being bizarly at the upper left where most calculators wrongly put it (=again, too far off for right hand).
Fourth, the division-sign can be set, as preference, to '/', instead of the omnipresent but confusing dot-line-dot, which way too much resembles the '+', 'x' and plus/minus.
Fifth, it can hide/show its 4 memory buttons. Do you ever use those? Neither do I, so drop them; cleans up the interface even more.
Sixth, it's available for both iPhone and iPad, and works particularly smooth in landscape mode on both.
Seven –at which I'll stop– yes it can switch off those irritating and pointless click-sounds and, indeed, it does have a full scientific keyboard as well, for those who need that (though that will kick out the full -but not the current– tape).
Finally, two minor flaws: scientific mode and the tape shouldn't be mutually excluding, and the full tape should be integrated into portrait mode as well.
