Unfortunately, a lifetime in the U.S. has left me with poor intuition for Celsius. The conversion isn't difficult to do in ones head and for laboratory work, naturally, it's just as easy to read one thermometer scale as another. For everyday life, weather reports, fever thermometer readings, thermostats and such, it is just a nuisance to convert from Fahrenheit and back. If someone tells me it's 15 degrees C outside I have to do mental arithmetic to know if I should take a sweater. Furthermore, from a purely logical perspective perhaps we should even consider using Kelvin.

It's a completely different story for distance, weight and volume. Metric measurement in these cases are more intuitive for me, and they are clearly superior too. Millimeters are so much easier to use than fractions of an inch (7/32 inch -- that's a ridiculous system). In the U.S., an ounce of flour weighs less than an ounce of gold. Who even knows how much a grain of gunpowder is in units anyone else uses (one grain is approximately 1/16 gram). There are three teaspoons in one tablespoon, but only two cups in a pint, 2 pints in a quart and 4 quarts in a gallon.

I'd be happy to switch from imperial to SI units for length, mass, and volume. I'll gladly switch slugs to kilograms and pounds to Newtons, but I will miss Fahrenheit.