Celsius: Where Metric Fails
I love Metric, but I think for human purposes, Fahrenheit is more useful, and actually closer to the convenience of metric:
0: water freezes
100: water boils
0: colder than Denmark
100: warmer than human blood
If I want to boil and freeze water: hell yeah, Celsius. But if I want to know how hot or cold it is outside, explain it to me in terms I can understand!
(Originally a comment on the Big Fat Blog)