I think it has to do with the devices refresh rate. To refresh so many lines of pixels probably has a slight delay while screen movement. I'm not an expert but you can see this distortion on slower refresh rate monitors.
My iPad straight out of the box with no settings changed is the smoothest iPad scrolling, or any device for that matter, that I have ever seen. In fact I have told people I was surprised how silky smooth the scrolling is. I didn't think the iPad 2 was bad, but my new iPad is noticeably better.
i.e. I don't see the problem you are describing. Might be time to take it in for an exchange