Here in the UK we have a mix of metric and imperial, but strangely it all seems to work OK.
The currency is now metric (since 1971) but personal measurements are feet and inches or pounds and ounces.
Distances are in miles and we drink beer in pints. Petrol (gas) is in litres and you can buy milk in litres or pints.
Occasionally you can still find a bolt which has a Whitworth thread, but that's another story and one for those who have an old British motorbike.

At the end of the day, I think it's just what you get used to.

ROG.