Thx LordBug and Bobbin for the reply
Now I know that the 100hz IS supposed to result in completely smooth scrolling, so I have to investigate further what the problem with my display exactly is... I'll try both your suggestions, but I'm having a hunch that it's my monitor which doesn't support 100hz properly at 800x600 (it's an IBM 17 inch from 5 years ago)... I'll see
Thanks for the suggestions!