As a long-time amiga user, I've heard about MorphOS many years ago. I could try it only when it became available for dirt cheap macs.
The most annoying things at the beginning were: 1) the lack of Workbench, 2) the inability to play modules with HippoPlayer. Now I can live without these.
And without 3) draggable screens, and 4) ability to move a part of a window out of the monitor.

The hardest thing is the update process from an iso image (CD drive is faulty) - it always needs a recall on how to do it.

Besides, it is a very nice system with the spirit of Amiga.