Copter-3.6.0 has been released as the default version for Multicopters and Traditional Helicopters.
The release announcement is here and includes the large number of changes: https://discuss.ardupilot.org/t/copter-3-6-0-released.
Thanks very much to the developers and beta testers who contributed to this release! We have put a lot of effort into testing this release and we hope that it will go smoothly but if you find issues, please report them in the support forums here and we will try and address them asap: https://discuss.ardupilot.org/c/arducopter/copter-36
(Ardupilot Dev Team)