So I figured I might as well jump in with both feet and change the policy, so now Director level employees may choose to use either and we will both supply and manage the machine of their choice.
However, recently the word came down from on high that we would be buying Macs for a few users whether I liked it or not.
There were a few Mac users, but we didn't manage their computers, they were personally owned. So we've been a PC shop for my entire time as IT Director.