Specifically, the old highlighter didn't support the "diff" format which was important for changelogs.
Changed the style from dark to light, since it's way too contrasty on a light background - makes it hard to scan both text and code.
And reduced the padding between code and content (mostly using the highlight style defaults)
Added a slight background shadow on code to visually offset the relatively light background color
Changed existing background color for <pre> to a slightly lighter shade, better contrast
Didn't create a custom *.ss style yet, too much work, and XML is good enough for now
Universal increase in font size
Use same font as ss.org for consistency
Remove unnecessary visual noise (borders, box shadows, etc)
Use Google PrettyPrint syntax highlighter for improved readability of code sections
Fully responsive, with hamburger menu
Add "section" linking mode to menu items
Add masthead for breadcrumbs, introduction
Improved styles for notice/info/warning messaging
