Responsive (re-sizeable) websites are something new, so it presents a challenge when it is a bit unknown to a designer or developer. It required doing research, seeing other site examples. It took a few years to envision some of the changes to the site, and only in the summer did we begin working on the project development. The site was fully re-coded. There were new features added that didn't work well on the first try, and then they were re-coded and re-tested.
Design-wise it was more about upgrading/improving the site, then making a completely different look that may confuse readers. Some of the challenges were how to incorporate the advertising banners that were not supposed to be re-sizable for ad standards, yet make the site stretchable and looking good.