It's pretty accurate. Believe it or not, one of our most infamous aviation near-disasters in Canada (the Gimli Glider) happened because someone made a mistake converting fuel quantities between metric & imperial.

My favourite thing is when we get to use awful combinations of both systems, like measuring out 15g of coffee for 12oz of water. Or having 26" bike wheels inflated to 30psi but attached to the bike with a 10mm axle. I especially love kcals and mmHg.