I own both KOF2001 (JPN version) and a 50 Hz. PAL system.
There is supposed to be a little sound delay because the 50 Hz thing as Atrophyed said, but I must say that I never noticed it in my Home Cart System.
Regarding graphics, there are minor graphics problems during the pre-fight intro printed on the PAL black bars at the top & bottom of the screen, but this problems automatically dissapears as soon as the fight starts.
Hope that helps
<small>[ January 18, 2003, 10:51 AM: Message edited by: ocsmod ]</small>