There are many changes in this version, and among them I want to point out a few that I consider important:
- No more support for old browsers like Internet Explorer 7 and earlier or Firefox 3.6 and earlier. This avoids many hacks, and makes the code faster.
- Mobile first- Responsive CSS is no longer in a separate file, but included in the core CSS file.
- Overhauled and simplified grid system, including more friendly to mobile devices where they scale up and down better. Grid system is using percentage instead of pixel, which helps in mobile websites.
- Buttons – “fewer but better”, per the documentation. Buttons look simpler/flattened.
- Moving Glyphicons to a separate repository, instead of integrating with Bootstrap. This should make it easier to use Font Awesome as replacement.
- “Hero unit” renamed “jumbotron”.
- Added new components: Panel, List group
- Submenus have been dropped.
- And many more changes…
There is no official release date yet, but I think we can expect the final version in a month or two.