Ink Ribbon went back to its roots; providing a barebone CSS starting point for designers who don't want Drupal's default styles interfering with their design. Combine it with other base themes if you'd like more features such as the ones mentioned below.
Moved the base theme to its own subdirectory in the project package.
Trimmed the reset so it only resets elements that actually need to be reset. (e.g. no longer set margin/padding of a div to 0 since it never has margins/paddings in the first place.)
Added a default margin-bottom of 1.5em to #console in layout.css.
Removed the unnecessary comment blocks from CSS files. Their purposes are already documented at the project page.
Rolled back an earlier change which added system message styles from the Seven theme. System styles now have the default core styles back, with some minor adjustments.
Inkribbon no longer overrides style sheets from core by default. Instead, it focusses on providing minimal but efficient base styles and encourages the separation of styles across different files. For example:
html-elements.css for generic HTML elements
layout.css for the page layout (page width, header, footer, sidebars …)
navigation.css for navigational elements (menus, tabs, pagers …)
