Back in the day I did some timing tests using the ST with Cubase and Notator, average midi jitter was around 0.2milliseconds, which is similar to the Octatrack*, the ARmk2* and AK* fare even better at around 0.08milliseconds.
TBH I think anything sub 2 milliseconds is acceptable to most people.
*Triggering internal sounds, I did not test external midi.