I remember trying one, many years ago. It required two diskdrives, and it was really crap.
I remember trying the game "Starball" (a pinball-game), and it ran really slowly.
I don't know why they haven't made a decent ST-emulator for the Amiga yet.. I don't think it would be much harder than making a Mac-emulator, at least not for running system-friendly TOS/GEM-software.
Here's a challenge for Amiga-coders:
Write an ST-emulator for the Amiga!!!