Especially when displaying measurement results, one usually wants to round to a certain number of significant digits, not a certain number of digits after the decimal point.
E.g. two significant digits
12.384 -> 12
0.4427 -> 0.44
75839.9 -> 76000
0.004958 -> 0.005
etc.
I'd like to see such a formatting option for numbers. Even better would be a general formatting string option like in printf() or perhaps python-style or R-style.