The new major version number doesn't indicate any deliberate API incompatibility.
We have endeavoured to avoid breaking existing APIs. However, pexpect is under new maintenance after a long dormancy, so some caution is warranted.
- A new [unicode API](http://pexpect.readthedocs.org/en/latest/api/pexpect.html#handling-unicode) was introduced.
- Python 3 is now supported, using a single codebase.
- Pexpect now requires at least Python 2.6 or 3.2.
- The modules other than pexpect, such as `pexpect.fdpexpect` and `pexpect.pxssh`, were moved into the pexpect package. For now, wrapper modules are installed to the old locations for backwards compatibility (e.g. `import pxssh` will still work), but these will be removed at some point in the future.
- Ignoring `SIGHUP` is now optional - thanks to Kimmo Parviainen-Jalanko for the patch.
We also now have [docs on ReadTheDocs](http://pexpect.readthedocs.org/), and [continuous integration on Travis CI](https://travis-ci.org/pexpect/pexpect).