Worked at Logica in the '80s when they had were engaged by Microsoft to port Xenix to other platforms. So played with it a little at the time.
For me it was my introduction to UNIX, the teacher would take a PC tower with Xenix into the room, each student group would prepare their UNIX exercises in MS-DOS as good as we could, and then we had a time slot to make them work on the tower.
Had it not been for FOSS UNIX clones, they were probably right.