To improve browsing performance, is it worth upgrading to iOS 5, on the original iPad 16GB Wifi? Currently, running an iPad 16GB Wifi only model with iOS 4.3.5. I have been noticing some slow redraw issues using Safari, generally when scrolling down length pages. I am seeing the checkerboard background, then the page renders.  Would upgrading to the latest version of iOS fix this or make it worse?  

Is there a way to roll back to iOS 4.3.5, should I find iOS 5 latest version to be worse?
The version of Safari that ships with IOS 5 has much better performance than the versions that ship with iOS 4, as reported in this blog post and this article. This increased performance may address the checkerboard rendering issue that you've mentioned. HTML pipelining was introduced in iOS5, and may help with the latency that results in slow rendering. Anecdotally, viewing web pages in Safari does seem a lot faster after I upgraded to iOS 5.

Regarding a rollback to iOS 4 if you don't like iOS 5 - cksum's provides some detailed info in this Apple.SE answer.