We experienced timing-related problems in early demos when running them on a more modern Amiga.
However, the worst was running software written for PAL mode. The chief complaint about these PAL games was that the audio played at the wrong speed. Major offenders were games that play lots and lots of sound clips, like Llamatron. PAL mode always messed up the length of the sound clips so they get cut off or played at the wrong pitch.
I had an Amiga 2500 which was the one that came with a 68020+MMU accelerator. I later upgraded it with the 68030 accelerator and Univ. of Lowell A2410 workstation graphics. I also still own an Amiga 3000T with a QIC tape drive with Amiga UNIX and an Amiga 3000 with a floptical drive. Playing old demos is a pain in the neck on these new machines.