Converting BEER to metric would be easy, they wouldn't even need to change the glasses as most pints poured are 0.5 litres once you discount the head. Better still, sell it by weight, no more sarky comments about whether you could fit a whisky in there...
I'm exclusively metric*, it's so much easier. I measure liquid in grams when cooking, more accurate than a jug, and a 1:1 conversion in metric. Also useful in other spheres: take a 55 litre windsurf board, you weigh 75 kg, you know you will sink it. Problem if it's in cu ft and stones.
* ok, occasionally I drive, and the numbers on the speedo have to match those on the signs. Also relative measurements with a tape measure, like hanging pictures at the same height: the number doesn't matter, but the tape measure has big numbers for inches and I can't be arsed to find my glasses.