Thanks to Bob Baumel, almost all the race courses in Oklahoma are done with kilometer splits only. For the marathon/half-marathon, the measurers usually provide mile splits and 5km splits.
The kilometer splits instead mile splits have been done for so long, the runners are use to it. I don't recall hearing any negative feedback.
It would be interesting to hear from Bob on the issues/problems/feedback as Oklahoma converted from mile splits to km splits !!