metric units are accurate and conversions between weight and volume become a breeze., but they are emotionless. If you say something is travelling at 10 metres per second ... everyone says so what. If you say something is travelling at 160mph, it conveys maginitude much better. It's similar with centigrade and farenheight I think. It took me 40 years to become comfortable with centigrade
I think having a mixed system like we have is the best solution. I mean, a measure of distance being how far a farmer can plough his field in a day is just wonderful i think