Firefox scrolls very well at 1024x768x24on my Win2K with only a classic Athlon overclocked to 950Mhz, my small experience is that it depends on the application.
What I'm amazed is how well iBrowse scrolls at 800x600x24 with a cybervision and a mere WarpEnding at 40Mhz. Almost as good! Still waiting to experience an Amiga with an 060 66mhz or PowerPC, I bet the scrolling is close to perfect. Talk about efficient use of resources.
