Most of the breaking changes are effectively bug fixes in the sense that the old behavior was either not what you would want or not what you would expect. The single most breaking change is the first one listed: removing new lines from line-oriented I/O functions – but it really makes these functions more pleasant to work with. The next two most breaking changes are actual bug fixes: one was a macro hygiene fix which a lot of packages happened to rely on the broken behavior of, and the other was to make new method definitions reliably take effect (#265), which is a huge benefit but also breaks some code that was relying on the old wrong behavior.