The issue is definitely caused by available, or rather non-available RAM.
On iPad 2, it shouldn't be much of an issue, I can open hfboards.com, swap to Asphalt 6, play a few rounds, swap back to Safari and scroll up and down, as fast as I want and not once does it need to recache
On iPad 1, it is another thing. If the memory is free, it won't have to recache once, when scrolling, regardless of how fast I scroll, but if it runs low on memory, it takes time to reload. I think what happens is, Safari creates a local copy of the website, but only keeps part of it in the RAM, so it takes a while to recache, as it stores the rest off the website on the flash drive.
Anyway, running a deep clean with XSysInfo can fix this issue on both iPad 1&2, as it frees the memory, so Safari keeps the whole website in the RAM, instead of just parts.
Seems strange though. I have a release day ipad, the first thing I did was hook up the wireless and browse a website, and it did it with nothing else loaded except Find Iphone.