I wouldn't touch metric with a 3.048-meter pole,
Actually, I've no problem with metric units and think it would be a great convenience not to have to buy two sets of sockets.
There is, however, one exception (and it's the one folks in the UK and Canada seem to have no problem with): temperature measurement.
While the centigrade scale is convenient for chemists, in everyday use the Fahrenheit scale's resolution more closely matches everyday human experience. Negative temperatures should describe a really, really cold day, not a typical Winter day in the northern latitudes. Zero to 100 Fahrenheit encompasses the range of what we experience in real life, unless you live in Antarctica or the Mojave Desert. Zero to 100 Celsius encompasses the range of liquid water, rarely relevant to whether or not I'll put on a jacket.