I also posted a response on Meta. The trashed logo and the vomit-inducing noise serving as artwork, as covered in other answers, seriously degrade the site's image and give it an amateurish appearance.
I can only assume that whoever worked on the Super User redesign had an axe to grind with this site. Aside from the general changes that affect all sites, many aspects of the Super User customization are actively bad; purposeless degradations rather than improvements.
Super User was not a site with "Cadillac" treatment; it was always a simple site. The changes shown are customizations for customization sake, not required by the theme change, and are very undesirable. Using the stock theme with the unaltered original site logo would be better than trashing the site as shown.