I am probably going to start another "range war" by bringing this up again. So let me start by saying that I really don't care which measurement system we use.
I like the English system of fractional measurement and I use it daily. I like being able to split increments into smaller units without getting ridiculous. I mean really, try splitting a mil into tenths!?!? Whereas a thirty second of an inch can be split into sixty fourths and you can still see the marks with the naked eye. But I also like metrics. Basing the measuring system on tenths makes the math so much easier and if you work to the mil, there is really no need for smaller increments.
What I don't like is this "mixed" system we are ending up with. There is simply no good way to convert inches to mils precisely. Yes, you can "get close" but not exact unless you want to end up having to measure everything in hundredths or thousandths of an inch and that is way too fussy for my taste.
But we have a problem here because most of our tooling is "English" and more and more, our materials are metric. 1/4" router bits and shaper cutters but 5 mil plywood. Dado sets that are calibrated in fractions so you can set up a 3/4" dado but the plywood is 19 mil, not 3/4. Arrgh!
I am dreading the day that all of our solid stock starts being processed in a country (not naming any here) that uses the metric system. It's bad enough that I don't have any tooling that matches the sheet stock thickness. OK, I know I can buy 5 mil groovers but metric router bits are not real common. Metric straight bits are available from some manufacturers. But what? Now I have to have two sets of tooling? And keep them separate? Scheech!