I find that theres lots to be looking at and thinking about in city riding; so doing the conversion takes my mind off what's going on around me ... so Ide like to replace the speedo dial with a dual dial to make life easier and safter ...
I know what you mean. I recently attended a Ducati demo day and test rode a tricolore S4Rs which had a MPH speedo and I am more conversant with metric.
On my S2R1K I am pretty accurate guestimating my speed and use my instruments just to double check things. However, on the test ride the combination of new roads, new bike, and ticket happy LEOs kept part of my brain watching the speedo and doing quick 1.6 times tables to ensure I was not ticketed and to compare accelerations, braking, etc. I am not great at math and these calcs were a pain while trying to enjoy the ride.
Oh by the way, the S4Rs is awesome! Anyone that has one is very lucky.