I like that Mathematica works with prefixes and units in lower case, except for a unit symbol "derived from the name of a person." ("NIST Guide to the SI," 6.1.2). I also like Mathematica works with units in the singular.
In[9]:= Quantity[0.0007, "inch"]
UnitConvert[%, "micrometer"]
Quantity[101325., "Pa"]
UnitConvert[%, "psi"]
Out[9]= Quantity[0.0007, "Inches"]
Out[10]= Quantity[17.78, "Micrometers"]
Out[11]= Quantity[101325., "Pascals"]
Out[12]= Quantity[14.6959, ("PoundsForce")/("Inches")^2]