The new version of Mozmill brings some under the hood changes to the Python back-end.
Further we have improved the handling of Python callbacks from within Mozmill tests. While the former version of Mozmill has only supported those callbacks for restart tests, you can use them in normal tests (Bug 538058) now. The only restriction is that the test-run has to be started from the command line client. Users with only the extension installed will not have access to this feature. In the future we will probably use it to implement handling of system level elements and events. Ongoing work can be checked on Bug 525060.
Another great enhancement we are proud to announce are the simplified steps to install Mozmill as command line client on Windows. The only requirement we have is the Mozilla Build environment. There is no need to install Python or the pywin32 extension in parallel anymore. Complete instructions can be found on MDC. A big thanks goes to Atul Varma for his contribution. You helped us a lot!
For more information check-out the complete list of fixes.