It is much more than just a scaler. eXtended Detail Enhancement (XDE) technology incorporates at least three different intelligent processing features, including contrast enhancement, color enhancement and sharpness/edge enhancement (this last one seems to be the most important for improved picture quality). "Intelligent enhancement" I believe means that the entire picture is analyzed, then enhancements are selectively applied only to those portions of the picture where needed, unlike traditional sharpness controls which affect everything. See this link for an interesting explanation of how old-fashioned edge enhancement works:
http://www.videophile.info/Guide_EE/Page_01.htm