Good news, although i'm not exactly thrilled with it.
MorphOS has been, for me, as fast as Workbench is, running on a humble 68040/25 and in some cases even slower (the menu system, just to name one).
Also, 68k apps tend to crash quite often.
So, AOS is still the number one choise for me. I run MorphOS mainly when i want to run something that doen't exist for AOS.