- box-sizing is now border-box
- The naming convention of all less variables has changed from camelCase to lowercase-dash-seperated
- Every form, input control or button needs to be touched due to the class changes, also anything that uses the Bootstrap grid system, this is also described in the Bootstrap migration guide
- All unchanged bootstrap default variables have been removed from the definitions.less
- All less mixins have been moved out of the definitions.less file into a mixins.less