Version 2.4 of the ArduCopter code is now available in the AP Mission Planner and in the downloads area. Although not as big a change as the 2.3 release, it still includes a respectable number of enhancements and bug fixes.
The default PIDs are optimized for a 3DR/Jdrones quad with 850 motors and 10" props. If you're using more powerful motors/props, start by turning down Rate Roll P in 25% steps.
Thanks go to the numerous contributors including users and their detailed bug reports, developers and testers. Hopefully all together this will add up to a nice smooth release!
As per usual, please post your comments, issues in this discussion. For enhancement requests for future versions, feel free to add them to the issues list. Note: you can "star" an issue to receive emails when someone comments on the item. On the dev side it helps us because we can get an idea as to which feature requests are the most popular by sorting by the number of people how have starred each issue.