The BWMA (http://www.bwmaonline.com/) exists to oppose metrication in the UK, and to promote (or preserve) use of the "Imperial" system of units. They're pretty well unhinged.
Imperial units are almost but not quite the same as US Customary units - except gallons, pints, tons are different. And the UK use stones for a person's weight not pounds...
From the website:
My grandmother (who would fit in with these people very well) blames the metric system for declining levels of numeracy. Apparently, it's too easy to convert between centimeters and kilometers, whereas anyone who had to be able to say how many inches there were in 12 miles and 15 rods in response to a verbal question from a teacher would know their basic arithmetic quite well, thank you. :)
It all depends on what you are doing. If you want to test your maths skills, by all means use imperial, babylonian or whatever units you like. I even knew someone who used a lunar calendar, converting all dates in his diary to and from this weird system. If you want to build a nuclear power station, or even re-fit my carpets then ThisAintTheRightPlaceToMuckAround.