Mathematica: The awesome Quantity system for values with units is everything the SysMLv1.x Quantity/Unit system should have been (and hopefully SysMLv2 will be). But it comes at a high performance cost!

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Dr Darren says:
If you are using physical quantities with units you can make them Quantity items across your entire project or application and enjoy safe units-aware computations with little extra effort.

And most other more primitive languages that can't do this aren't ... the Wolfram Language!

Ever "painted" the units for a value in your user interface instead of interrogating a deep Quantity for its Unit and using that? Don't! Be DRY and use the Single Source of Truth (SSoT). Get real and use a units-aware system like Mathematica with completely consistent propagation and automated conversions.
Too good to be true? Well, unfortunately as of MMA 13.0.0.0 there are currently two major performance hits (reported already to Wolfram Support):
Mathematica: Compile won't work with a Quantity with units
Mathematica: Use of UnitConvert (or even just multiplication or division by a unit Quantity) MASSIVELY slows the calculations down!
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Related notes
[CAVEAT, GOTCHA, TIP, WARNING]{INFORMATIVE} GOTCHA: Mathematica v13.2+: Operations on "DegreesFahrenheit" °F and "DegreesCelsius" °C are now performed using Kelvins (K). CASE: Naive percentage operation gives answer relative to Kelvins. Use "DegreesCelsiusDifference"/"DegreesFahrenheitDifference"!
[GOTCHA, WARNING] Mathematica: GOTCHA: MMA distinguishes between Kelvins and KelvinsDifference
[TIP]{INFORMATIVE} QUDV in SysML refers to: Quantity, Unit, Dimension, Value. It is strongly influenced by the International Vocabulary of Metrology (VIM).
[TIP]{SUGGESTED} You can use a ValueType to document how a value of a certain quantity kind should be measured (in a particular system, in a particular organisation, or according to an industry standard).
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