I know a fan has listed the differences between different version but we do not currently have a difference version for the current version online. I do not know specifically where it is.
There have not been any rule changes but we have changed the wording in some sections to make it clearer and have added a few new terms to make teaching the rules easier. Fire Zone is one such term. This has more to do with preparing for the Storms of Steal rules than correcting things in AtB.
In the future we will be highlight the sections in the index that have been updated in the new version.