I remember when I was getting ready to buy an ATF55 thinking about the fact that it had a metric scale. And actually considering it as part of the decision. After the fact it turned out to be no big deal. Once I moved on to the TS55 (not REQ) I did use an add on imperial sticker. Again no big deal but just more convenient for me. On my TSC55 I would prefer to have an imperial scale, but not a deal breaker. The thing I actually don't like on the TSC55 is the dual on rail off rail scale. I was always have to think about which one I should be using (haven't used it very many times yet though).
I don't think I have ever used the scale on the 1400 router. I use gauge blocks to set depths. So it could probably not have any scale at all.
I would prefer an imperial scale on the HL850. That is something that I find to be a real nuisance and generally something that I need to be exact. So converting 1/16" to whatever in mm is a place to introduce error.
I think there are several metric or imperial usage methods at work in NA. Very user dependent. But in light of my first line, "I remember when I was getting ready to buy an ATF55 thinking about the fact that it had a metric scale", it probably makes sense for Festool to switch to imperial in NA. Simply so that buyers are not put off by thinking that the metric scales will be a big problem. The degree of whether or not the scale is a problem for the user will vary. But after someone starts using the tools, I think the scale problem starts to diminish in ones thinking. At least that was the case for me.
Though I would prefer to work and have everything in metric I am just waaay to tuned in to thinking in imperial.
Seth